1) Relationship Screw-Ups: Most people focus on the standard issue bad boyfriend or bad girlfriend, but unless they’re all stabby or trick you into impregnating them, you’ll be fine. Well, unless you stay in a really shitty relationship for way, way too long. I mean, if you’re on say, year 4 and don’t have a date set for the marriage, you should be asking yourself if you’re just wasting time. Also, if the two of you are fighting like cats and dogs while you’re not married and have no kids, RUN. Run like the wind while you can. Don’t be the dumbass who thinks you’re going to get married and everything will change.
However, the really bad cases are the good ones you let go because you want to screw other people or worse yet, the horrible ones you marry. The good ones you let go? You’ll think about them for DECADES afterwards and even if they get divorced, they may remember you as the guy who broke their heart so they’ll want nothing to do with you. The horrible ones you marry? The divorce will be awful and may even turn vindictive; it will damage your ability to trust the opposite sex and especially if you’re female, you’ll spend years getting over it. Oh, and if children are involved? That’s when it can REALLY get ugly.
2) Unprotected Sex: Is it a good idea to be abstinent before marriage? Absolutely. Are most people doing that? Nope.Instead, they’re having sex with every relatively attractive person they can find whom they can talk into it.That can be problematic because unfortunately, we humans tend to highly value short term rewards and discount longer term benefits. That means having sex without a condom seems like a great idea in the moment, but less of a wonderful thing when you end up having a baby with the hot, but extremely bitchy stoner chick you met at the frat party last night. Then there’s STIs. I knew a guy who got incurable Herpes in college. Good luck getting a date on Plenty of Fish when you slap that on there.
3) Smoking: Sure, smoking makes you smell bad, turns off members of the opposite sex who don’t smoke and gives you lung cancer, but then there’s what it does to your face. You can get by for a long time without seeing any negative effects from smoking and then one day, your face is a catcher’s mitt.