Most of us keep a list of things we'll do once we feel ready. The class you've wanted to take since March. The conversation you keep pushing to next week. The post sitting in drafts.

None of it is waiting on ability. It's waiting on a feeling, and the feeling hasn't shown up.

Fifty years of research shows that confidence gets built out of things you've already done, which means it arrives after you act. Waiting to feel ready is waiting for the last step to come first.

Why we're confident about some things and not others

Psychologists tend to skip the word confidence. They use self-efficacy, meaning your belief that you can do one particular thing. The belief belongs to the task. You hold a separate one for every task in your life.

That's why it comes out so uneven in the same woman. You can be:

• calm driving through a city you've never been to, while unable to send back an order that came out wrong

• the person everyone calls in a crisis, and four days silent on one text

• fluent in a second language, and lost on the phone with your bank

• the one who plans everybody's birthday, and unable to say you'd rather not go

So saying "I'm not a confident person" is really a sentence about a handful of situations, not overall.

The four places it comes from

Albert Bandura, a psychologist at Stanford, found four sources that build the belief.

• Doing it yourself. Bandura calls this mastery experience and it's the strongest of the four by a distance. There's a catch. Easy wins build a belief that falls apart the first time something gets hard. The kind that holds comes from struggling through something difficult and getting to the other side.

• Watching someone else do it. Seeing another person manage something lifts your sense that you could manage it, too. How much it lifts depends on how similar to you she seems. If she looks nothing like you, it barely moves.

• Being told you can. Encouragement does help. But Bandura found that words are much better at knocking a belief down than building one up. One comment about what you're bad at can outlast years of praise.

• What your body is doing. A racing heart before something hard gets read as proof you can't do it. Bandura's finding is that the racing heart means nothing on its own. What matters is whether you read it as fear or as getting ready.

Now look at which of those you can arrange today. You could watch someone, ask a friend for a pep talk, or work on your breathing this afternoon.

The thirteen-point gap

There's one more thing here, and it's specific to us.

Two economists, Christine Exley and Judd Kessler, gave thousands of people a short test and then asked them to rate how well they'd done, from 0 to 100. Women rated themselves 13 points below men who had gotten exactly the same score. The average answer was 53, so that gap is close to a quarter of it.

The women in that study got slightly more questions right than the men did. Asked how many they thought they'd gotten, the men guessed around 11 out of 20 and the women guessed under 9. They did better and described it worse.

The test was focused on math and science. When the researchers ran the study again with a verbal test, the gap disappeared. So this isn't a setting you carry around everywhere. It shows up in the subjects you were taught you're worse at.

Where to start

Bandura's advice was written for people trying to build confidence in somebody else. It works just as well on ourselves.

• Pick one specific thing. "Be more confident" has nowhere to start. "Say it at dinner on Sunday" or "book the beginners' class" does.

• Make it hard, but possible. It has to be something we might not pull off, or there's nothing to learn from having done it. It also shouldn't be something likely to go badly again and again, because early repeated failure does real damage.

• Compare against our own last attempt. Bandura is specific about this. Success gets measured by how much we've improved, rather than by whether we came out ahead of anyone else.

• Keep track of what we've done. The evidence is the whole mechanism, and we forget it remarkably fast.

So the list doesn't need us to become a different person first. It needs one item off it, chosen on purpose and attempted while it still feels too early.

Once it's done, the version you tell will probably come out smaller than it was. That's the thirteen points again. Write down what happened, at the size it happened.