Failure leads to success, I once heard. I guess all I can tell you is that if you feel that you're not good enough in a game, all you're missing to do is learn from other people that are equally skilled or better than you. I know it's not easy not to be a sore loser. It's actually some hard shit to accomplish there, but I suggest you should change your attitude towards these kinds of situations. Instead of getting upset, look up to the bright side of things. What you did right, what you need to improve, which part you beat others in, etc. and you should have some random activity you can do for when you start getting stressed about the subject matter. I always keep this quote in my mind while I'm playing, "No matter how good you are at something, there is always someone in the planet who is better than you."