Cool request! Thanks @mkz!! Sorry if these are all really cliche!!!
  1. Length of relationship is no indication of how healthy the relationship is.
    I was with someone for 6 years in a toxic relationship. I went on 3 dates with one guy and was more honest with him than I've ever been with anyone else.
  2. It's always better to fight--but choose your battles.
    I grew up in a broken home where my parents fought constantly, so I tend to shy away from starting shit with a significant other. I'm more likely to just let it all bottle up and let it explode later. This is bad because it means that I'm not very good at fighting clean. I don't know how to fight properly so I just unload everything that's ever bothered me. I learned it's much better to just speak up and risk a small fight vs a world shattering one later.
  3. You teach people how to treat you.
    Seems obvious, right? You let someone treat you badly once or twice and don't say anything, they figure "oh, she's cool with it". Many times, I was in fact NOT cool with it and it lead to unhealthy behaviors and relationships. It became a lot easier as I got older to recognize what I want and how I should be treated.
  4. Your friends are right about someone like 99% of the time.
    Makes sense. They aren't seeing this guy from the same rose-colored, heart shaped glasses that you are. It wasn't until after I broke up with a boyfriend that my two best friends said "oh, thank god! He was such an asshole!!" And I was like "TELL ME NEXT TIME, YA IDJITS". So now they're better about it and I'm less likely to date morons.
  5. Cut off ALL communication when you break least initially.
    That 6 year relationship I mentioned earlier? Yeah, should have been over when we broke up after year 5. Buuuuut after we "broke up", we still talked every day and that lead to us getting back together after a month "apart". No bueno. It just lead to an even messier break-up a year later.
  6. You don't have to like his mother.
  7. You need to like at least most of his friends.
  8. Your sole function shouldn't be trying to "fix" him.