I think we need to learn to forgive and treat ourselves with compassion. Also develop deeper understanding of ourselves and life in general and use it as the basis for accepting ourselves.
For development we also need to look at ourselves critically and evaluate. Who are you, what did you achieve so far, what else can you achieve? Sometimes we need to give ourselves negative evaluation and work hard to develop.
Life is a combination of accepting oneself as we are and self evaluation, sometimes negatively. We learn for a very long time to differentiate what to do in every other situation.