Both are hard to learn. But it gets harder if you find yourself not able to control yourself and your emotions, as it will only prolong your losses, hence winning long term remains a struggle.
Well both may be difficult but I think it's best to settle for the conclusion that self control is more difficult since basically more gamblers struggle to maintain it. Another thing is self control can be related directly to long term winning because practically speaking gambling addicts have the least level of self control and as a result they also tend to be the ones who lose most in gambling.
Most times winning on a long term also requires luck aside from self control because gambling isn't solely dependent on analysis and experience. Self control basically Helps you keep track of your habits.
Actually, I think self-control can be done as long as we have strict discipline, with that there will be no behavior that leads us to risky actions. It's just that this is a problem that often occurs and I think it's because those who can't maintain their self-control when gambling until they experience something that is detrimental to themselves, after all, it's their own fault, not the casino's. Gambling that involves luck in terms of winning is indeed very appropriate, but I don't think there is luck that can make us get a win that lasts in the long term, because luck usually only happens occasionally and doesn't last long. Maybe if it lasts long it's not luck.