Not naive or unrealistic but I really genuinely thought that if you cared about someone even if you didn't end up with the fairytale you could end up as friends. My first love and I spent his last Christmas together (before he passed away) over a decade after we broke up; another love and I are still close even after they married someone else. Of the four people I've loved in my life only one was unrepairable.
I do this with friendships too. And herein lies the problem, I try and keep things connected even after there is no life left. I've stayed in friendships way past the expiration date. Even after someone's shown me they're not a good -let alone great- friend I've tried to revive that connection because there was still some love left.
You can't keep everyone that's ever been important to you in your life,Ironically a friend who is no longer a close friend told me that. Still brilliant advise. So when a friendship is dying and someone stops carrying I'm learning to let them go... not easy... but you can't revive dead horses.
otherwise you won't have room for people that might become even more important.
Another ill advised habit along the same lines is when someone was upset with me I would try and find out why and fix it. Then recently a very wise person told me: sometimes people are just mad and/or nuts... so when they are angry and coming at you don't charge into the situtation and try and fix it. People's anger at you isn't always (read: often) about you. If someone is that mad and you didn't kill their dog, screw their sister, or take their life savings maybe they are angry and you just happen to be in their way.
Rational people that have a valid point talk things out like adults, mad people are mad and instead of trying to reason with a charging bull run the other way or at least get out of their path so they don't trample you.
There are plenty of people in the world that will treasure our friendship/relationship, will argue rationally, will even fight fair, but for those that show us they don't or won't, we need to stop reviving and know when to let things go ... and when to stay out of the way.