When you are gambling for fun and you do that only during your leisure time, you will be able to have self control over your gambling activities, because you are working. People that don't have jobs shouldn't gamble, because there is a high chance that majority of them will be gambling for profit, and that will make them game excessively.
Only gamble with an amount of money that you can afford to lose and stop the game at the right time, so that you don't get tempted to chase your losses and lose more.
Gambling at leisure time doesn't guarantee anything in gambling. If you play when it's not your leasure time or not, it doesn't gives you self control. I see self control as something you learn own your own, you develop it and works for you, if you don't have a self control and you gamble when you are doing nothing, you will develop anger immediately you lose money but if you have it right from beginning, you don't see it as anything and you don't even bother about the loss.
It's easy to build a strong mind if only you are not gambling with problems in your hands. Imagine that you are gambling and you have zero expectations and you are not planning your potential win to solve any of your problems, believe me you will not care about when you lose money. It's only when you have developed plans in your mind on how to spend your money it does make one angry especially when you loss a huge potential cashout.