The fear of losing money will cause regret when you win a bet. In my opinion, it is just an illusion that crosses someone's mind because they are unable to bear the loss when they lose. In fact, if he was able to think objectively, winning and losing are part of gambling, maybe this small win would not have happened.
People that do have the fear of losing are gamblers that want to see themselves making money but don't want to incur any loses. Gambling need some orientation to those kind of people because their is no way you are not going to incur loses in betting. This is normal and we should not expect to be making consistent profits every time you take a bet. Gambling is not an activity for the lazy ones or those that don't want to see any loses in their bets but want to be making consistent profit. When you have the strategy and luck coupled together, the chances of making consistent loses as gamblers will be minimal.