Wants to have the fun back

Heres my problem.
I play a lot of games. Not so much that i play lot of games but i play the ones i have a lot. And i get really into them. If i believe the game is not going my way; I'll get angry and shout curses at the tv. I see that what im doing is wrong and counter-productive, but i cant help it. I'm not a sore loser by any means and enjoy a good tough fight (so to speak) but if i cant perform to my (impossibly high?) standards i get frustrated and aggitated.
My wife sees this (or rather hears) and tells me to calm down or turn it off. But when no one is around to remind me, i go back to being angry.
It wasnt always like this. I used to play these games to relax and have fun. Now i feel as every game is important even tough, deep dpwn, i know its not. Theres a little more to this, but this is big problem im facing: How to go back to just playing games and having fun.