This just begs the question of how to distinguish brick walls from insurmountable obstacles. Persistance is certainly a virtue, but there's a very large problem with asking successful people how to succeed. Many successful academics will tell you that you will succeed, provided you sacrifice enough of your time and happiness. Asking them creates a bias though. You'd better also ask the many, many post-docs who quit, burnt out and miserable, after being denied a faculty position for the umpteenth time. If you can't find some systematic difference you can use to succeed, then you're faced with a gamble. And human psychology pretty much guarantees the market will overvalue that gamble.