Being a Humanist requires a certain amount of self-awareness.
If you aren’t willing to critically judge your own behavior, you have no way of improving.
Be aware that you aren’t perfect.
Reflect on how you might do and be better.
Take constructive action to actually be better.
I find that having a sense of self-worth is made easier when I know that I matter because I regularly take action that matters to others.
But the number 1 skill? Self-directed learning.
Without a willingness to learn how to be better, you won’t improve.