I try to deal with loss by taking a break, often after a loss you are upset or angry and so it's not good to keep trading. I take a walk or play some video games to clear my mind, then when I'm clear minded I get back to it and deal with my loss by making a profit
It depends if the loss takes place in gambling no one can help for that as gambling need fortunes.In trading, if the loss happens need to think about it, better to keep focussing on opportunities rather than thinking about the loss, don't regret about the loss look for the opportunities.