I dont think the problem lies in the winning/losing, if anything gambling just amplifies on character..if you are greedy by default I can guarantee you that gambling will eat you alive, and if you are the type with discipline then you will have the control of your money habits and you won't lose yourself in a win-lose situation!!
So a disciplined character is a very important attribute to have in the gambling industry.
Sometimes many newbies get their gambling life ruined by their first big hit winning, this is what mostly happens to those newbie that will think that he have suddenly developed a strategy to keep hitting such big winning on a consistent basis, this make things a bit tough for them along the way since they come to a point where resistant becomes an issues and at that time they will begin to lose uncontrollably.
I think the losing would have even a bigger impact on a newbie because they will chase their losses to try win back what they lost...unlike winning which would still need testing to see if strategy still works and no need to go crazy with it.