TL;dr : Couple of days ago I walked away from a fight and now im feeling terrible for it.

Backstory : Recently broke up with this girl, I have been seeing for 6 months (mostly based on sex) and she was very upset, telling me that I treated like a whore, a piece of meat and threw her away. Anyway she is so upset that to get back at me she called one of her "white knight" friends claiming that she got physically abused by me. And this guy is furiously calling me to meet with him to fight. Now I am not much of a fighter but during this kind of situations I feel like I can take down anyone anywhere (adrenalin rush). After some furious yelling and threatening each other on phone, I felt like that is I need to take this fucker down no matter. But I realised that If i fight no matter what happens, I will be the guy who got manipulated by a girl into a totally unnecessary fight. And as you may know even the winner of street fights are getting harmed most of the time ( broken fingers,hands, torned clothes etc.) So instead I choosed to walk away, knowing that they are going to perceive me as a coward, which I dont give a fuck to be honest.

The problem is instinctively I am feeling I should have fought with this guy no matter what. It is such a strong feeling that almost telling me if you backdown from this you will backdown from any fight in future. What is TRP saying about this kind of situations? Is it a mistake to walk away from a fight?