Here's some things I learned living with my ex:

1) Small issues really matter and they can build up into resentments over time if they aren't addressed

2) Talking about the relationship often is a good thing to do

3) Differing future plans and expectations can be really bad for the longevity of a relationship

4) It's really important to appreciate your partner and do things for them and the relationship

5) Living in a very small apartment with someone who really needs a lot of space is a bad idea, especially if you're unemployed and home all the time.

6) It's easy to lose your sense of identity in the relationship if you don't work to maintain it - especially if you have weak personal boundaries

7) Mental health issues can really fuck up a relationship - depression (this was me) anxiety and insecurities can be damaging

8) It's easy to stagnate, neglect yourself and live with unhappiness because it's comfortable

9) Physical intimacy is super important, it's a bad sign if this starts to go down hill

10) It's an amazing feeling to feel loved by someone else and to be intimate with them, there's nothing quite like it. I miss it greatly.

11) Trust is so important, even if it's small things. If you say you're going to do something for your partner do it. Don't be lazy about it because it just gradually erodes trust over time if you keep not keeping your word. Even if it's just something like picking up your clothes off the floor.

12) If your partner makes something creative, really show them how much you appreciate it and praise them for it genuinely. I'm guilty of not doing this and really regret it now.

13) Don't rely on the other person to be your source of happiness/self-esteem, it isn't healthy