You could be happy and think you will have a great day and later you will find out that it's not your lucky day at all, if you are happy and having a great day don't think it will contribute to your success in winning in the gambling, you don't have control and sometimes we tend to be careless when we are full of emotion, it's better to bet when you are more relaxed.
Winning a bet is about your strategy and how lucky the gambler is. I agree with you, when one can't control his/her emotions when gambling, it can lead to losing much Funds. You can come to a Gambling hall feeling happy and probably lose on your bets. From my experience, I win most of my bets when I play for fun