You don't have to part enemies. Sometimes, we simply outgrow a partner we thought we'd be with forever. There is no sin in this.
People become adversarial with each other, because they try to make something "work" with another who either wasn't a proper and good fit for them in the first place, or they grew and evolved in ways their partner couldn't keep up with.
Breaking up with someone you've loved should feel as painful for YOU as it is for THEM. Most of us won't let ourselves experience this, so we stick around and beat a dead horse, until we can build up so much resentment and hostility, walking away from 'em feels easier.
Is this healthy? Is it respectful? Is this the best or most loving way to exit a relationship bond? Ask yourself, "how bad did I let it get with this person, before I decided to give up on getting it right with 'em?"
Years ago, I broke off a relationship with someone I really cared for. It was painful, and I cried right along with him, when it became clear that we couldn't build a more significant bond. I hadn't stopped loving him~ I just knew it wasn't an optimal fit for me.
BOTH of my eyes got conjunctivitis from copious tears, and I awoke the next morning with my eyelids glued together. I intuitively remedied this problem with a bit of antibacterial ointment on the inner corner of each eye that morning and night before bed, but it was still a bizarre experience.
People tend to think that if they part, it's gotta be as enemies. They stay just long enough to despise each other, and the beautiful love they once shared at the start, is lost even from memory. Personally, I think this is a tragic shame~ and yet I believe far too many are terrified to be 'alone with themselves,' it's the most common outcome we see.
You CAN still love someone, and let them go. You just have to be prepared to mourn and grieve that loss, rather than scapegoating that individual you once held in your perfect fantasy of "happily ever after," for your unhappiness or discontent, and harshly punishing em for letting you down.
Try and remember: It takes two to Tango, and two to tangle~ and accept that every relationship you have teaches you far more about yourself and how to better navigate your life, than you knew before you met that person. So in fact, they've been one of the many gifts you'll receive during the course of this lifetime.