Timing is everything in gambling, If game is at peak and if you leave at the right time with profit.. than we called them as a smart gambler
You are right timing is the main factor which could bring some reward and we can this was great peace of gambling but reality is that it's not easy for all people to let at the winning when we don't have any goal there. We must put some goal there than it would be easy to give up.
If we have a control on timing, when we want to leave the games, then the problem would be solved that we could leave when we want to break the game, Actually, main problem is that when we are playing gambling without break and use our money continuously on betting. Then in the end, definitely our loses are more than our winning, and most of the time, i see we could lose our whole money.