I think I'm one of those people who limit themselves, but I'm gradually (very slowly) growing out of it. The main reason, I think, is because it's painful to work hard and not see it pay off. Even if you know if you kept patient you'll reach the end, sometimes, if feels like the end is so far away.
I have a cousin who's the opposite of me in that regard, and your words are true as he has long caught up and surpassed me with pure "perseverance," and I respect that so much about him.
It's better to be in good terms with yourself, see the issue most people have is they belittle theirselve, I was once like that too. But I got out of it.
So you also should change your mindset just like your cousin