We, humans, are menifestation of our thoughts and everybody's personality is basically menifestation of what he thinks about himself.
I wanna add one thing here, those who want to become something but cannot change their thoughts and ultimate personality, this quote suits them; "Fake it until you make it", or more better to say, "Fake it until you become it".Today I came across to this way of thinking twice. Earlier I read a beautiful post by @jaynie where it was described, what we think, we eventually become, and now same concept but different wording.