Cheatinggg..

It's obvious how do you not see it!
Okayy, people you need to chill if your man or woman cheats on you dont frinkin' panic and have a go at them it's hardly going to change things! It's most likely just going too have the opposite effect?! You should really just do the least exciting thing first and get it out of the way by asking them if or why they did it. If they don't have a reason then well ... You decide what you wanna do! end it if you like. But, if they have a reason and it envolves you not paying much attention too them or anything like that it's most likely not as much there fault as it is yours. I'm sorry but face it, that's just how it is. People make mistakes don't they. 

Anyways, so if they have a reason and it doesn't envolve you then... Have a little bit of fun with it get all the details or make it dramatic, act like it didn't bother you at all. ( ;) ) afterwards you take your time to move on. ;D and hope the next one works out better. (Ohh, and never ever ever flip out at the girl(s) or boy(s) that they had cheated on you with 'cause to be honest unless that person was your bestfriend or family relative or the closest friend you have: then, one; they're really not worth it.
Two; they probably don't know about you.
Or three; it's just really not their fault that your man or woman came along and took your place for a night or two (or more ;/).