If you lose a game, you shouldn't be in a bad mood, instead try to play chess with a bigger enthusiasm. Although it's easier to say than done, because
I start a tournament badly, usually I finish it in a same way. But of course I had some tournament when I recovered and finished it in a good mood. And this is what you should try! Even if you start a tournament badly, try to play your best chess and if you do, your self-confidence will be back!