She Cheated On The Wrong Dude
To avoid reacting like the above dude, something to ALWAYS keep in mind is that her vagina isn't yours and it never will be. As soon as she leaves, you no longer have access to it and when she's out of your sight, she can give it to whoever she wants to. Despite proclamations of endless loyalty and move, realistically you don't know is she's sharing it or not. So what I'm telling you is to mentally condition yourself to never get so caught up in a woman that once you learn the fact that she's been sharing herself with someone else, that you don't lose it. Sure you will feel a bit of emotional pain, but you have to put yourself in a position to recover quickly. Never, ever build your life around a woman and make her your life's mission. Always have things you are dedicated to way above women. If she breaks bad, if you've kept yourself up and you're a fly dude, sure you'd be hurt a little, but then in another way, you wouldn't lose any sleep because you know that opens the door you to pick from the other women who've been eyeing you.