What you said is 100% correct. While gambling it is not so easy to control your emotions in both situations so I always go with some fixed small amounts for each session. In that way I can play my game without worrying much and if I lose also can enjoy my game still. If one gamble to make a money then it is quite dangerous and at the end can lose lot of money in gambling so gamble carefully.
To controlling your emotions while playing games is a bit tough. But we must control our games another wise we will end with the big loss. And yes I agree that when we are in the long run win or lose it's very difficult to control our stakes. We will become greedy in that time. So small amount betting is the best choice and we can able to control our loss.