Friedrich Nietzsche put it in one line in 1889: "What does not kill me, makes me stronger." It's a favourite on posters and gym walls. More than a century later, a team following a national sample of American adults for several years checked whether it's true.
It's half true. People who had been through some hardship in their lives had better mental health and more life satisfaction than people who had been through a lot. They also did better than people who had been through almost nothing. And when fresh trouble hit, the ones with some past adversity were the least shaken by it.
That kind of strength is also more ordinary than it sounds. After a loss or a frightening event, a steady path, with sadness and a few bad nights and then a fairly quick return to everyday life, is more common than was long believed. It's standard equipment. Some people come out of hard times with something extra. The questionnaire most used to measure growth after trauma covers five areas, and one of them is called "personal strength".
So inner strength is less a hidden force waiting to be released and more a capacity you build, the way muscle grows: some load, some recovery, then a little more load. Ahead: the one sentence that steadied people's hearts under stress, what lifting weights does for low mood, why failure teaches less than you'd expect, and why a hill looks less steep with a friend beside you.
1. Be on your own side
Strength starts with how you treat yourself after a setback. After failing a test, people who were encouraged to go easy on themselves studied longer for the next one than people given a boost about how clever they were. Harshness feels like discipline. Kindness keeps you in the game.
The usual tip is a sticky note on the mirror: "I am worthy." For people with low self-esteem, the ones it's aimed at, repeating a line like that can leave them feeling worse. The mind argues back, and wins.
Talk to yourself the way a good coach would: honest about what went wrong, and clear about what to do next. Kristin Neff's shows how to be kind to yourself without letting yourself off the hook.
A coach uses your name, and so can you. People given a few minutes to prepare a speech, who thought through their nerves in their own name ("Why is Sam nervous?"), felt less anxious and gave better speeches than people who used "I".
Next time you slip, say what happened in one plain sentence, then what you'll do differently. "I snapped at him because I was tired. I'll apologise and go to bed earlier."
2. Treat stress as fuel
A racing heart before something hard feels like a warning. It's also your body getting ready. When people were told before a stressful task that this arousal helps performance, their hearts pumped more efficiently, their blood vessels relaxed, and they paid less attention to threatening information than people given no such advice.
The same reframe raised real exam scores. Students preparing for the GRE, the graduate school entrance test, were told that feeling anxious can improve performance. They outscored the others on the maths section in the lab, and again on the real test one to three months later. Hans Selye, who spent his career on stress, gave the good kind its own name: eustress, from the Greek eu-, good. Kelly McGonigal builds a whole book on this shift in .
Words help too. Before singing karaoke, giving a speech or doing a maths test, people who said "I am excited" out loud felt more excited and did better than people who tried to calm down. Nerves and excitement share the same racing pulse, and relabelling it is easier than switching it off.
Willpower works the same way. The old idea that it runs out like fuel was put to a big test: 23 labs and more than 2,000 people, and the effect came out close to zero. What people believe matters more. Those who saw willpower as limited flagged after a draining task. Those who saw it as plentiful kept going.
Before the next nerve-racking moment, tell yourself, "This is my body getting ready", or say "I am excited." Then start.
3. Go a little past your comfort zone
Strength grows at the edge of what you can handle. Seneca put it two thousand years ago: "Fire tries gold, misfortune tries brave men." The team that tested Nietzsche's line found the benefit came from some adversity, and a lot of it did harm. So pick a stretch you can recover from.
Even monkeys show it. Young squirrel monkeys given short spells of mild stress grew up calmer and more curious, with lower stress hormones, than monkeys raised without them.
The edge is often closer and friendlier than it looks. Commuters asked to talk to a stranger on the train had a more pleasant ride than commuters who sat in silence. Other commuters, asked to guess, expected the opposite.
Lifting something heavy is the most literal stretch. Across 33 controlled tests with 1,877 people, strength training with weights, bands or body weight clearly eased symptoms of depression, whatever people's health and however much they lifted. The lift in mood came whether or not they got much stronger. A is an easy way to start at home.
Feed the muscle you're asking to grow. Across 49 controlled tests with 1,863 people, extra protein added a modest boost to the strength and muscle gained from lifting. Meat, fish and eggs make it easy.
And when a stretch goes wrong, take the lesson on purpose. People told they'd answered a question wrong learned less from it than people told they'd got one right, even though both could work out the right answer. A failure stings, and the mind tunes out. They learned just as well from other people's mistakes, which suggests the fix: look at your own slip the way you'd look at a friend's.
After a hard experience, write about it. Across 146 randomised tests, writing down your thoughts and feelings about something difficult had a small but real benefit.
Recovery is the other half of the deal. Even small night-to-night losses of sleep predicted more anxiety the next day. The muscle gets built in the rest after the effort. If you're already carrying more than you can recover from, the strong move runs the other way: put something down, and ask for help.
Choose one small stretch this week, such as speaking up in a meeting or saying hello to a neighbour you've never met. Afterwards, write one line about what it taught you.
4. Set goals that pull you forward
Nietzsche wrote a second line a few maxims later: "If we have our own why in life, we shall get along with almost any how." It holds up too. In a national sample of US adults followed for 14 years, people with a clear sense of purpose lived longer, even after other measures of wellbeing were taken into account. Viktor Frankl, who survived the Nazi camps, came back to that line again and again in Man's Search for Meaning.
A clear goal gives that why somewhere to go. Over decades of testing, people given a specific, challenging goal did better than people told to do their best.
Break the goal into steps small enough to finish. Each one you complete is evidence that you can do hard things. Albert Bandura, who spent a career on confidence, ranked that kind of first-hand success as its strongest source.
Keep score where you can see it. Across 138 tests with nearly 20,000 people, tracking progress helped people reach their goals, and it worked best when the progress was written down or shared.
Grit gets a lot of press. Across 88 groups with 66,807 people, it predicted performance only moderately and overlapped heavily with plain conscientiousness. The part that mattered most was steady effort.
Write down one long-term goal and three steps towards it. Do the first step this week, and tick each one off on paper.
5. Choose your company
The people around you change how steep life looks, and a hill proves it. People standing at the foot of a hill judged it less steep when a friend stood with them. Just thinking of a supportive friend had the same effect, and the longer and closer the friendship, the gentler the slope looked.
A hand helps too. Married women facing the threat of a mild electric shock showed less threat response in the brain while holding their husband's hand, and the happier the marriage, the bigger the effect. A stranger's hand helped a little.
Strength also flows the other way. Among 846 adults followed for five years, stressful events predicted a higher risk of dying, except in people who'd helped friends or family in the past year. For them, the link disappeared.
The famous newspaper ad for Ernest Shackleton's Antarctic crew, "Men wanted for hazardous journey… Safe return doubtful", was almost certainly never printed. What happened next was real. When their ship Endurance was crushed by ice, the 28 men stuck together through months on the ice and on Elephant Island, and every one of them came home in 1916.
Before your next hard thing, call or sit with the person who makes hills look smaller. And this week, help someone with something practical.
Strength you build
Nietzsche was half right about hardship: it can make you stronger, in amounts you can recover from, with rest in between and people beside you. He was right about the why.
"Courage" comes from the Latin cor, the heart: the pounding one you feel before something hard.
Pick one stretch this week, tell your racing heart it's getting you ready, and take a friend to the foot of the hill. It'll look less steep from there.
Carrying more than you can recover from? How to Build Resilience When Everything's Falling Apart — what to do when the load is too much.
Harder on yourself than on anyone else? 10 Tips to Fall in Love with Yourself — self-compassion in ten everyday habits.
Know someone who thinks strength is for other people? Send them this. Then go for a walk up a hill together.
Disclaimer: This article is general information. For advice about your own health, talk to a qualified health professional. If your mood has been low for weeks or you're having thoughts of harming yourself, reach out for help today.
Affiliate Disclosure: This article contains affiliate links. As an Amazon Associate, All For Life earns from qualifying purchases, at no extra cost to you. We only link to products we would recommend without the commission.
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