My dad told me again to "let go" of my obsession of what others think of me. what is he trying to say?

A few days ago, I : Heard someone say "what people think of me is none of my business." this may be what your dad is trying to tell you. By obsessing over what other people think of you you actually give them a lot of power and you can make yourself feel miserable. Try focusing more on how you think of yourself and whether you appreciate your gifts, qualities, strengths and whether you can be kind to yourself.