How to quickly forget a loss - make a much bigger loss. I dont think that losses should be forgotten. Its experience, valuable experience. Unforgotten losses mush sober up gambler from taking reckless decisions in gambling. Huge losses should try to stop greed, as they must remind that a person can quickly raise and quickly fall.
One moment bigger loss becomes critical to the budget.

But of course losses is an experience we have to get. It is impossible to become a winner without losses. The problem may be with the first loss and with the biggest loss, but even such losses are very important to become stronger and smarter.