1. When one person asks, “Why do you love me?” and the other struggles to answer readily, or provides a canned reply instead of saying something sincere.
2. When your significant other says something so deeply offensive, you have to wonder whether they like—let alone love—you enough to justify staying together.
3. When you realize that the lust you once felt during the early stages of dating isn’t quite there anymore, and even though something more remarkable and lasting has taken its place, you ache to resurrect the blind, obsessive passion that first drew you to each other. Knowing that you can’t definitely sucks.
4. When you wake up from an awesomely sexy dream starring someone other than your boyfriend or girlfriend and the awareness that you can’t make your fantasy a reality because you’re in an exclusive relationship brings you down, at least until you drink your morning coffee.
5. When you’re thinking about a lifetime of fidelity with the person you adore, and you just can’t shake the skeptical, how-the-fuck-do-couples-actually-do-it? thoughts from tainting your heart.
6. When something about your partner’s past is revealed that makes you cringe out of disdain for who they once were, or what they once stood for.
7. When accepting the fact that your partner is a living, breathing accumulation of every choice they’ve ever made—including the decision to fuck all those other people (before you saved them)—proves more difficult than you wish.
8. When one person is caught lying about even the most innocuous thing and that minor fib inevitably undermines their credibility, at least temporarily.
9. When you fail to comfort your partner in the aftermath of a devastating life event or a typical bad day, and then someone else—a friend, a sibling, or a parent—steps in and proves way more helpful, kind of compromising your position as Most Important Person in your lover’s life.
10. When a tough period or a nasty fight inspires someone to wonder, out loud, what life would look like if they’d never broken up with their ex.
11. When you both have to acknowledge that you’d probably benefit from an afternoon apart, doing separate things, even though you don’t get all that much time together.
12. When jealousy prevents you from being genuinely happy for your significant other, or makes you act like an asshole rather than being supportive.
13. When one person behaves in a mind-blowing way, forcing you to question how well you really know each other.
14. When someone’s new friend or hobby totally turns the other off, and you both start to doubt how much you have in common.
15. When the idea of having kids leads you to draft a mental checklist of the traits you hope your baby does (and doesn’t) inherit from your significant other.
16. When you dare to “go there”—to that place you know better than to visit because doing so will lead to the worst kind of hurt—and then quickly regret it, but the damage is already done.
17. When an apology rings false, exacerbating an already prickly situation.
18. When someone secretly isn’t all that amped for a special occasion or a date night that’s been planned forever so they try to feign excitement but it’s frustratingly obvious that they’re not in the mood or as present as they should be.
19. When you realize that maybe you’re the one who’s behavior is toxic to the relationship and you’re not quite sure how to make things better.
20. When you think about what exactly keeps you together and the truth isn’t all that romantic. The glue might just be something banal, like shared stubbornness, or a mutual appreciation for Game of Thrones and a consistent desire to go to bed early. And yet, it works.