Remember all the promises you’ve ever made, write on a piece of paper and try to fulfill them as quickly as possible. If for objective reasons this cannot be done, then try to at least just apologize to the person.
Achieve goals. This will not only allow you to start respecting yourself, but also develop your self-confidence, willpower and increase your motivation level. To begin with, simple goals can be set, which do not cause much difficulty. But then the complexity has to grow, and with it, your self-respect. Try setting some difficult goal with very limited deadlines. By coping with it, you will get an unprecedented charge of energy and self-satisfaction.
Objectively evaluate yourself. Perhaps the reason for the low level of self-respect is that you treat yourself too prejudiced. Try describing yourself without resorting to prejudice. You will see that there are enough sides in your character worthy of respect.