It depends the most on the details of the situation. For example maybe the loss was massive then it will take a longer time to forget and if it is smaller it will be faster. It is healthy to do it this way. There are those people that are in denial about the consequences of their actions and they say that they can forget big losses fast. This is very unhealthy, never do this. It is a child's attempt to run away from reality and it never works. This usually leads to other compulsive behavior and mistakes. I particularly only had a big loss a few times and it did take some months and in some cases years to swallow it, but this doesn't have to be restricted to gambling. You can also make very bad investment choices which at the time sounded good.
I don't see a reason why loss should be massive when in real sense you are meant to gamble with what you can afford to lose. You see something, many times without numbers we are the architect of our own problems. 99% of gambling addiction can be avoided but we tend to turn blind eyes into somethings that could have been avoided in the first place. There is nothing that is going to cause harm to anyone if you gamble with small amount of money.
The assumption that there is big money to be made in gambling has made many people to sink in this casino thing. I have made my peace that there is nothing huge to be made from casino that's why I put the little I can give to the casino. There are people that find ways to win huge amount with small amount, they are smart but I'm not good at it and I don't bother myself with it but if you check their strategies, they look smarter than some people that bet in huge amounts of money.