For buying shares ,as an investors, they should do the due diligent.
In gamble you should know how to control yourself.
Diligent work applies very well to sport betting (researching a team/player, etc) and poker (overall working on your game, putting tons of hours to studying various concepts)
Self-control is usefull and mandatory there as well, but its mostly useless in games like dice and roulette, where self control wont help you win, so you might as well go full-retard.