Well, to be honest, it's easy to say this.
However, the actual application of this changes depends on the situation that we're dealing with, and that's why we have discovered the best way to control our money and emotions.
Just do it because if it works properly on us, we have to apply that most time so that we'll still be alright.
We need to practice since controlling your emotions is one of those factors that affecting our decision making, and we all know that a single mistake can cause a huge harm with your finances, if you know how to control then better to keep practising that kind of discipline it leads you to a enjoyable gaming/gambling.
And you are right, do it if things working well to avoid hurting too much with your deposit balance..
Control the amount of the bankroll including the emotions.
So yes, if it's not hurting it's fine but if it's hurting that much not just emotionally but also the pocket.
From the simple way of controlling them, it will become a habit and that type of gambler will have an understanding on where he's being too much.