Fighting and/or approaching conflict in a healthy manner.
During one of my early fights with my GF (now wife of 15 years) I was surprised that even though she was still mad, she clearly said “I’m upset when you did X, because of (something in her past). I know that past event is not your fault, but I’m still feeling some kind of way, we should talk later after I’ve processed a bit.”
Wayyyyy different than my past relationship. No silent treatment, no hiding emotions and exploding later, firm about feelings while taking accountability, honest apologies… it’s great. We still have conflicts, and even yell from time to time, but they are productive in the end.