Then why do you play?
When I win, my attitude varies from good / finally / glad we didn't throw to "that game was awesome!"
When I lose, my attitude varies from "pissed, how could we have thrown that" to "well that team sucked, what can you do" to "damn that game was close (and I enjoyed it)".
Of course, you're occasionally going to be pissed about losses. Sometimes you get sick of getting garbage teammates. There will also be wins that are stomps that derive no enjoyment. The somewhat close games where you actually get to play a full game though, should be enjoyed... if not at their conclusion, I'd hope you enjoy the game while you're playing it (and then are let down that it's over, win or loss). If you're not, maybe you need to take a break (or play normals / ARAMs) and see if it changes your view.