1. When you’re in the middle of talking dirty but one person gets completely flustered and tongue tied and says something totally nonsensical and/or utterly unsexy.
2. When you’re wasted and intent on having sex but you’re both so sloppy that it’s a total mess.
3. When your flesh slaps together in such a way that your bodies create some reallllly weird sounds, and, try as you might to shift about, the unsexy orchestra just won’t stop and you can only hope that your partner doesn’t really care.
4. When someone gets legitimately hurt in the process of trying to shift from one position into the next and you have to weigh the promise of an orgasm against the certain pleasure of icing your injury immediately.
5. When you realize, mid-sex, that you definitely have to pee and you have to channel every morsel of willpower within to stick it out without urinating all over your significant other.
6. When you’re not really enjoying what your significant other is doing down there, but you don’t really have the heart to articulate that their technique isn’t quite working for you since they seem so into whatever they’re doing.
7. When he’s trying to penetrate and her vagina’s drier that the Sahara desert for whatever reason and he’s forced to wonder why she’s not feeling aroused.
8. When either party farts. And it stinks.
9. When one person breaks out into song randomly or says something so out of the blue and mood-killing that the other’s forced to confront the reality that their partner isn’t exactly feeling it at the moment.
10. When the sudden awareness that there might just be a tampon inside one of you forces you to stop humping and fish around for the thing just in case before resuming the sexy play or moving onto another activity altogether.
11. When one person can’t help but wonder, ephemerally, if this is how their parents did it and the very thought of their mom and dad humping puts their libido in reverse.
12. When one person wakes up feeling so turned on that they can’t help waking up their partner, who’s really just desperate for a few extra z’s and not exactly the most willing fuck buddy so the sex, if it happens, is totally meh.
13. When you forget to pack your favorite lube so you have to use saliva, a poor substitute for the premium, water-based stuff you’re used to, on that romantic vacation instead.
14. When your excitement over that position you’ve both been dying to try evaporates instantly upon execution because it sucks for at least one of you and you’re forced to shelve disappointment and resort to something a bit more routine.
15. When you either person starts thinking about a past lover or an ex mid-sex and almost says that other person’s name out loud.
16. When anal enters the conversation because one person’s desperate to try it but the other one’s either terrified that it will hurt or make them “feel gay.”
17. When her period is late and you have to pause and think about the real world implications of having sex with someone regularly.
18. When someone gets called out for faking it and/or exaggerating the pleasure factor to a ridiculous extent.
19. When one person’s craving a little post coital cuddling but the other’s in a serious rush to get on with their day.
20. When one person comes within seconds because they’re so damn horny and they just can’t help it.
21. When one person is super randy but their partner doesn’t want sex because they jerked off one too many times earlier that day.
22. When someone suggests a threesome and the other person interprets it as a sign that they’re not satisfying their partner properly.
23. When you realize that, in spite of the chemistry between you, you’re not 100 percent aligned in the bedroom, so you’ll both have to grit and bear it through certain acts for as long you’re together. 
