As a motivational speaker, I meet a lot of people who walk around believing something negative about themselves that simply isn't true. And this is dangerous, because often we believe it enough to actually make it come true. For example, if you walk around thinking that you are stupid, you won't trust your ideas, so you never speak – you don't trust your intelligence so you do what everybody else says to do – you don't think you can, so you don't try – and eventually, you come across as stupid. Many of us have established a belief based on feelings instead of thought. I get it – I've been there – and I still spend a lot of time fighting those old habits.
I found a fellow motivational speaker's post about this very subject. I found it helpful and comforting. And maybe you will too.