Says who? You can win with your high level of emotions, because losing and winning when gambling depends on luck, not your emotions, so someone who is emotional when gambling can win if its time for them to get lucky.

The problem will start after the first win, because anyone who can't control their emotions can easily be controlled or manipulated, even by the casinos and machines, most times, casinos will give you chance to win to hinder your thoughts about casinos and gambling.

For someone with a lot of uncontrollable emotions, they will easily think that they will win their next game again, and with such belief they will want to increase the amount they want to risk on the bets.