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.
I think that you are right because whenever you win gambling it will give you joy and happiness so that will motivate you to gamble more but in order ways when you lose in gambling also that something that happened that happened in gambling when you lose is that you like to recover the money you lose and that to motivate you to gamble again so two things is involved both winning and both losing
I would say that someone who is obsessed with gambling then simply usually they always feel addicted when they win and if they lose then usually they will be curious, which when you win then the victory can be a motivation for you to continue the session in the hope of returning to victory like that again, and when you lose then usually yes the inability to accept the reality of defeat will be felt by them which in addition they put curiosity to always try once again in the hope "maybe one more try I will win".
So actually whether you manage to get a win or you end up losing it is two situations that still make you continue the gambling session, there is no urge to stop at all because the level of consciousness has begun to thin out which makes you fall and get carried away by the situation, and this is why it is always recommended not to overdo it in terms of dealing with gambling and also not to overdo it in terms of hope for victory, it all depends on the mindset of a gambler.