Being hard on yourself and being disciplined are different things. One yells. The other just shows up.

Self-criticism and discipline get mistaken for each other because both feel strict. The difference is volume: one talks constantly about what kind of person you are, the other says nothing and simply starts the work at the agreed time. Harshness burns energy you needed for the task. Discipline is quieter and cheaper than it looks from outside.

When you catch yourself in a round of commentary about your own character, stop and ask what the next action is. Do that action for ten minutes, badly if necessary. You will find the work got done without the speech.