Trading is like a game, someday you win and someday you lose. And the best way to deal with losing is by learning your mistake that led you to lose your money. Once you learn your mistake then you can go ahead and continue with your trading.
And the most common thing that happen we must gonna be sure for everything that we wanted to be for example the way on how you may able to learn here by your experience so this is where you may able to deal with loss.
You don't have to deal with it to be honest, you just have to accept it and think of how you could make more profits rather that getting depressed on what just happened on your profits, because if you are going to be a negative thinker after a failure, then you are not going to be a successful person, unless if you are going to let that failure be your teacher to be a better one and to avoid making the same mistake again.