Just read an article on the Dunning-Kruger Effect. As the author Inchauste explains "As you grow at that skill, you begin to better evaluate your skills. Again, pretty logical reasoning here. If you know more about something, you know more about what you are doing wrong and how to improve it". Therefore if you don't know much i.e. you're unconsciously incompetent, you won't be able to assess yourself properly and are likely to overestimate how awesome you are.
So in that sense being self aware and having a bit of doubt isn't a bad thing...so long as it doesn't stop you from trying!