The only way I found out to control one's greed in gamble is not to play at all. When we all gamble, we all have the same issue, and that is we don't know when to stop.
Either decide a prefixed amount of your profit and loss, and stop when you have hit either of the boundaries. For this you need to have a very solid and stable mental state, else you'll keep on playing either to increase your winnings, or to win back what you have lost. In both the cases in the longer run, you'll be at harm.
This always happens to be in Poker, even when I am in 10x profit, I don't stop playing and eventually loose it all.
That is always going to happen if you dont change your habit. Thats what happened to me and I have ever won until 1 bitcoin when the price is less than $500. Thats probably the highest that I have ever got from just 0.1 bitcoin deposit, then greed was what made me to continue therefore I lose everything including what I have deposit so far