Nobody ever really succeeds at anything for which he does not have passion.  To make it to the top, there has to be a burning desire, a willingness to pay the price of study, perhaps loneliness, and certainly a tough-enough hide that what others think doesn’t really count.  Whether your interest is—doing medicine, making money, succeeding in a given sport, or living for God—, without a passion for what you want to do, the flame goes out, and the journey becomes too arduous and difficult.