What little voice in your head fills you with doubt?
Once you identify it, trace back to where it originated. Was it a critical parent or teacher?
Was it the bullying voices of peers. Over protective friends or family?
Once you know the origin ask yourself if there is any evidence to prove it might be correct.
My guess is that whatever evidence there may have been in the past is not valid now. Spend some time finding evidence to the contrary. It will dilute that doubt.