You keep your promises to everyone except yourself
Think about the last time you told a friend you would meet them at a certain time. You probably turned up. Maybe you were a few minutes late, maybe you sent a message from the car, but you went. If a colleague needs something by Thursday, they usually get it by Thursday. Most people who struggle to keep running are not unreliable people. They are reliable for everyone else.
The promises that slip are the ones made in private. I will go out tomorrow morning. I will do three this week. I will start properly on Monday. Nobody else heard them, so nobody is waiting at the corner when they quietly lapse. The only person who notices is you, and you notice more than you let on.
Every promise is also a piece of evidence
When you tell yourself you are going to do something, you are doing more than making a plan. You are also asking yourself to believe you. That belief works a lot like the trust you have in anyone else. It is built out of what has actually happened before.
If a friend cancelled on you most weeks, you would still like them. You would also stop rearranging your evening around their plans, and you would hear the next invitation with a small private shrug. That is what happens inside, too. After enough mornings that were promised and then slept through, the next promise arrives already discounted. You say I will go tomorrow, and some part of you hears it the way you would hear that friend.
This is why starting again can feel heavier than starting the first time. You are carrying a record. It is worth being clear about what that record shows, though. It does not say you are the kind of person who never follows through. You plainly do follow through, for other people, all the time. What it shows is that the promises you made to yourself were bigger than the days you made them for, and that you have been treating your own word as the one you are allowed to break.
Make the promise smaller than feels respectable
Trust between people gets rebuilt slowly, through small things done when they were said. The same is true here. You do not repair your belief in yourself with one dramatic week. You repair it with a promise so modest that keeping it is close to certain, and then you keep it.
That might be ten minutes. It might be putting your running clothes on and going to the end of the road. It should feel almost embarrassingly small, small enough that you would never mention it to anyone. The size is the point. A promise you can keep on a tired, irritable, rained-on evening is worth far more right now than an ambitious one that depends on a good day turning up.
If you feel like doing more once you are out there, you can. That part is a bonus. What you promised was the ten minutes, and the ten minutes is what counts.
Notice when you keep it
People are very good at noticing the promises they break. They tend to let the kept ones go by without comment, especially when the promise was small. Ten minutes does not feel like an achievement, so it does not get recorded as one.
Try recording it anyway. Not in a spreadsheet, and not as a streak you then have to defend. Just a moment of honest acknowledgement when you get back in: I said I would, and I did. That moment is the evidence you have been short of. You would give a friend that much credit for showing up when they said they would. You can give it to yourself.
Over a few weeks something shifts. You say I will go tomorrow, and it lands differently, because the last several times you said it, you went. The promises can grow a little at that point, at the speed your record supports, and no faster.
When you do break one
You will. Some evenings the small promise will still be too much, or life will take the hour before you get to it. When that happens, treat yourself the way you would treat a friend who is usually good for it and missed once. You would not decide they were hopeless. You would assume something got in the way, and you would expect them on the next one.
So make the next promise straight away, and make it small. One missed day is a broken promise. Abandoning the whole thing because of it is a second, larger one, and it is the one that does the real damage.
You already know how to be someone people can rely on. You have been practising for years. This is only a matter of putting yourself on the list.
Written to encourage, not to diagnose. If something hurts or feels wrong, please speak to a doctor.