Two things: perspective and wisdom.
When you are in the middle of things sometimes it’s hard to have perspective. I look back at people I parted with who I cared a lot about and the only thing that is true about all of them is this: I felt like I could not get past them at the time, and then time passed, and I’d eventually look back and think “how the fuck could I have even ever really liked them to begin with”? They either were shitty to me or boring as fuck to talk to or both.
The other thing – wisdom. You really should not allow anybody into you world that doesn’t make you feel stronger and build you up. If being with this guy was bad for your physical and mental well-being, then he shouldn’t be allowed To be more than an acquaintance in your life. Definitely not a mainstay. Plain and simple, he has to be a part of your past.