Everyone is a manwhore or slut, even when they're not
The Wedding Crashers line "Let's get hopped up and make some bad decisions!" is the unspoken collegiate mantra. It's a bona fide breeding ground for bad decisions. But in college, they don't count as bad. They're just decisions! And this is the time you're supposed to make them, so in a way, casual hookups aren't really judged the same way as they can be in adulthood.
Just accept the fact that along with your social security number, another thing you'll have down cold during your stint in higher learning is how to pull of the most discreet walk of shame possible.
… So it's very easy to justify cheating
I mean, it's not. But it is. And it's also not. Because, well, you drank A LOT. It will never happen again. And didn't he/she hook up with that guy at the band party last week anyway? Plus, it's not like you had sex. Well, you did, but you used a condom. So does that even really count as cheating? Who cares, [insert person you hooked up with] lives on the other side of campus, he/she will never be at the same dining hall as you. Right? Whatever, you drank a lot.