I'm not an expert in this field, but your statement seems wrong to me.
Our brains release endorphins AFTER a positive experience or outcome, not before that. The expectation of a positive outcome doesn't necessarily lead to our brains releasing endorphins.
Controlling your emotions is easier said than done. I don't believe that emotional control is the most important thing when it comes to winning more at gambling. You could make perfectly logical bets and still lose money. We have to remember that gambling is about luck, not about emotions and logic. Just keep making small bets and gambler for fun. That's my way of dealing with my emotions while gambling.