You can be able to control your emotions very well and still not be able to win when gambling and this is as gambling isn't an activity that you can do everytime and expect the same results. Gambling is a game of luck therefore the more lucky you're, the more you're going to be winning when gambling. Having control of your emotions is a good thing as it'll make you not to get out of control and make wrong decisions that'll make you not have a good chances of winning.
Being disciplined when gambling will help you alot as it'll make you to not be over gambling or spending above your gambling budget therefore not being a good gambler and later becoming an addict. Emotions can make you to not be lucky when gambling, when you allow your emotions to control you. You won't be in control of the decisions that you're making and it increased the chance of losing your money.