Just accept that we all are part nature and part nurture. I suspect your good friends accept you as you are; some probably really like you as you are. It is also kind of relative; Hang out with the some people and you will always feel stupid or smart. I think you should focus on doing things that you and others find very interesting. There is a famous line from Dune that basically says "fear is the mind-killer"; generalize that to "thinking too negatively about yourself can lead to poor outcomes".