Everyone believe in themselves when it's come to gamble. But the hold'em poker is much more complex game which requires lot of qualities such as poker and probability theory knowledge, strong intuition, hell of experience and guts importantly. However being math genius isn't enough for this game, it's close to chess but there's luck factor which can not be ignored. Other than those, I believe it requires strict discipline and mindset to be successfull over the long run. Lot of decent players are dead because of lacking these last properties.