Whenever I win or succeed in anything tho, I always say 'Thank you God' even though I didn't even pray for that specific thing and worked really hard to achieve it. 
That is what we will say if we can achieve a good result. But we might say, "Oh, damn, it should not happen to me 
Praying can give a positive feeling to someone and that increase confidence. But gambling is at a grey side of our life, so when we pray, we ask GOD help to help us win the game. Sometimes, GOD will allow us to win, but the other time, we will lose. We can let people pray or do whatever they like to win the games.