You could always do what I do when I feel down, get together with some friends, get high, or drunk, and watch something funny, you will be physically incapable of remembering the bad shit, like seriously, your brain will be unable to put the bad shit into your conscious mind, and all you will understand is what you are experiencing in the moment, good food, a good movie, or random adventures with friends, play cards against humanity, or apples to apples.
Not advocating illegal activities or anything, but I mean, where I'm from it's a totally normal thing, but if you live somewhere where you would face jail time I wouldn't want you to do something to make your life worse.
Other than that, loud angry music, sitting alone, thinking about things in your head until you get it all sorted, then go back to living as normal... OR if you happen to find calm soothing music more enjoyable go for it... Though usually when I'm angry I can't stand calm music, I need something that suits my mood, at least for awhile, then as I calm down I make a new playlist with classical music and shit, and listen to that.
Fact is, you can only deal with this kinda shit the way you can deal with this kinda shit. I know what betrayal feels like, never been cheated on, but I have been stolen from and lied to by women who've said they loved me, I have been screwed over by a lot of other people over the years too.
Now I have herpes, trust issues, and bad credit, but hey, what can ya do eh?
Life is after all, just your body dying, after you hit 18 or so, it's just a series of diminishing returns, then you die.