Like anyone of us here won't be greedy on a win, i know how many times ive played a game again with my capital back once I win a game and that's cause I felt luck so I want to try again, let's admit it it's not so easy to walk away especially if you have been winning, everyone gets greedy at some point.
If it works for you fine, you can continue with that. Try to be a little more strict it would help you a lot.
This i will admit the joy of wining give motivation to continue no matter how you try to back out from the game it's hard to pull out, it take extra ordinary discipline person to stop because the spirit will tell your to double what you have won if continue .
Greed is always the order of the day for gamblers just some happened to control their own that is where individual difference and management and decision play a vital role,as some may find it difficult to control themself when the gambling is favouring them not know losses is ahead , greed is like addiction once your build up with it in heart very hard to go out of it, but the necessity remain that one need control greed if possible abstain from it entirely.