You cannot win gambling when you don't have a self discipline, a self control. In one game you just have to be a formal Player to get the best move. If you have it all I'm sure people get luck every turns to wins.
In my opinion, in gambling there is never a clear consistency so I agree with you that it's particularly hard to win in gambling without self discipline.
Even if you have self-discipline,you can't always win in gambling.The percentage of winning is just very little compared to losing.Sometimes if you're really unlucky that day,you will only lose for sure.So gamble only what you can afford to lose so you won't feel so frustrated whenever it turns out negative.