1. You start to see yourself through someone else’s eyes, and are often wondering what you could do to be a better person to them.
2. Someone else’s schedule and needs become more important than your own, even if you know that they shouldn’t be.
3. You learn what you can and cannot tolerate in a relationship. (You also learn that you’ll be inclined to bend on these things if you really, really love the person — but that it’s a bad idea to do so.)
4. Someone becomes attractive to you for something much more than their body for the first time, and you realize that what they look like is the least important thing about them.
5. Everything starts to seem secondary to experiencing love with someone, even things that you used to be completely immersed in.
6. You catch yourself in raw, unfiltered moments that only loving someone can bring out of you.
7. You realize that having a crush on someone and being in love with them are completely different, because in a crush you can erase or ignore all of the impractical or less-desirable parts of what being with them would mean.
8. You absorb entirely new recipes, cultures, music, and inside jokes into your personality, without actually realizing you are taking them on (or imitating them). You always said that you weren’t going to become that person who is obsessed with everything their SO likes, but you absolutely are.
9. What you are actually doing with this person matters infinitely less than the fact that you are with them for the first time in your life.
10. After you meet the parents for the first time, you start to understand that it is at once not nearly as scary as you thought it would be and infinitely scarier than you could have anticipated.
11. You learn what it means to fight healthy, and fight for something more long-term than just who wins this particular argument.
12. You become part of a team and can understand disagreeing about something even though, at the end of the day, you both just want what the other one wants.
13. The night spent not sleeping because you haven’t heard back from your SO becomes less a ridiculous image of the desperate person in a relationship, and more a reality.
14. You understand that loving someone and wanting to be with them more than anything may not be enough to override fundamental differences.
15. Your friends will start to see you as part of a couple instead of just an individual, and will remark on how nice it is to see you out and about on the nights that you do end up going out by yourself.
16. The person that you love will break your heart and, even though it has always felt like that would be the end of the world, you realize that life isn’t over.
17. You also discover that the more powerful relationships often take several false starts before you can actually break up once and for all.
18. You become mature enough to realize that, even though you love this person very much, you ultimately love yourself more and want to protect the things you had before you fell in love in the first place.
19. Because of all that your first love taught you, you are ready to find someone new to share it all with, even if you won’t be as surprised by the person you become when you’re head-over-heels again. 
