My best advice is to find the fine line between things you can change and things you have to accept, and then walk on both sides of that line with a sense of humor.
For instance, my confidence comes from wearing clothes I feel good about, which is something you can change and build and redevelop. But in order to feel confident about clothes I like, I have to feel confident about the body I have. Like I’m almost 6’ and I’m a bigger girl and I actually dwarf people when I stand next to them, which has taken me YEARS to get over. But I know that I can’t change my height and I can’t change my body and frankly I don’t want to change my body, so I have to accept that this is who I am and that is okay.
And if I ever feel uncomfortable I just laugh about it because if I can find humor in my flaws then no one can touch me. Instead of falling into the mindset of “wow, I look like a cave troll,” I’m like “wow, I am the same size as a baby giraffe basically and that is fucking bad ass, do not cross me or I will beat you to death with my absurdly long neck” or whatever.
Find something you can change about yourself and change it with vigor, but hold onto the things you can’t change and know that they are an integral part of you and they do not make you a lesser person.