Why is it easier to keep promises to other people than to myself?

That asymmetry is not a character flaw. It is a structural problem, and structural problems have structural solutions.

What is actually happening

When you promise someone else, there is a second person holding the other end of the rope. They are expecting something. The discomfort of letting them down is immediate and social, which is one of the most powerful forces in human behaviour. When you promise yourself, the only person who knows is the person who already wants off the hook. The judge and the defendant are the same person, and the defendant always gets a sympathetic hearing.

This is not weakness. It is how the system works. Even extraordinarily disciplined people use external accountability to reinforce internal commitment. The discipline looks internal from the outside, but there is usually a structure behind it.

The witness problem

A promise lives or dies by who is holding it with you. A commitment you make only in your own head exists in the same space as the excuse that will replace it. You need to move it out of that space. Tell someone specific what you are doing and when it will be done. Not for their benefit, for the mechanics. The social discomfort of reporting back is the same force that makes you show up for other people, borrowed and redirected at yourself.

The identity problem

There is a second layer. Promises to other people feel like character. Breaking them costs you something about how you see yourself in relation to the world. Promises to yourself often do not carry the same weight because you have not decided yet that the version of you who keeps them is who you actually are. The belief and the behaviour are supposed to reinforce each other, but one of them has to move first, and usually it has to be the behaviour. You keep the small promise before you feel like someone who does, not after.

What changes things

Start with something small enough to be undeniable. Not the version of the promise that requires a perfect day and unlimited motivation. The version you could keep on a bad week. Keep it once. Then keep it again. The identity follows the evidence you give it, and you are the one producing the evidence.

Then find a witness. Not someone to manage you, just someone who knows. The people who understood where I was and what I was working toward were rarely in my immediate building. Being specific about what you are actually doing, not the title or the category, attracts exactly the right kind of accountability. Vague goals get vague company.

You are not less disciplined than the people who seem to keep their word to themselves. You are probably working without the structure they quietly have in place.