Having a loss in trading is something that must be faced by all traders, so it must be mentally prepared when starting trading. The best way
to deal with losses is by using the stop loss feature, making repairs for any mistakes, using capital gradually and do your research before
starting trading. If the method I mentioned was successfully realized, then I'm sure the amount of loss experienced gradually decreases.
It can even rarely experience losses.

Losses are what a trader can not wish away because it must come but how to handle it is different from person to person. But for us to be happy when we lose is to reduce our risk. If your risk is reduced, you can accept any loss that comes in your trade. I just let go my loss if it comes.

When I made mistakes or when I lose big amount of money in trading, I make losing very painful. What do I mean by that? I simply embrace the mistakes that I did, I fully understand why I lose and it is because of my lack of planning and also there are things that I do not yet know and I need to learn it. There are many people who not giving time to their loses, losing is part of trading so expect that there are really times that we can lose our money.

There are psychological effect if we will not handle our losses very well, we also make sure that we should journal every our trade for us to avoid the mistakes that we can make again. Backtesting is also important and traders should be aware of it because it is one of the trait of advanced trader who practicing by reviewing the recent and past price action of different kind of charts.

We can become a strong trader if we can fully embrace our losses in trading, we should treat the losses as opportunity to grow. We can become a trader where we can avoid major losses and maximize our returns if we will find the lessons that we can get from our losing trades.

This question has been asked many times, but then I understand coz you are a beginner.

You should also search for similar threads like this if you really wanna know.