This post isn't about that fantastic song by Elle King (seriously, check it out), but rather my ex's. I've noticed lately there is an expectation by some that you can't or shouldn't be friends with your ex's. I think that's crap.
Now, I have to make the usual disclaimers that this is not a universal truth. I have friends who learned that their spouses were going to be featured on "To Catch A Predator," and others who were the victims of intense physical or emotional abuse. Other were with convicted felons. These are absolutely not situations where your ex should in your life. Let's use common sense.
Something that is a universal truth is that every relationship ends in a break up or death. I'm not trying to be morbid or anything, it's just a fact. People split for a variety of reasons, but presumably they had some kind of intense connection at some point. There was time and emotion invested in it. It probably wasn't friendly when it ended, or it was friendly, with accepted differences and agreement that it was time to move on. Things change at that point, and you stop seeing each other naked, you don't cohabitate, etc. It doesn't mean that you can't be friends anymore.
Including Diana, I've had about four great loves in my life. (Maybe five, but the first was so immature that I'm not even sure it counts.) The previous relationships vary from marriage to something not easily defined, but they were real, they were intense, and they were important to me. Today, I'm still friends with them all, they've all met each other, and we're all adults. I credit Diana with not feeling threatened by this, but also for understanding that these are people who can't just be undone as a part of who I am. She even has the running joke of her "Thing 2" T-shirt (from Cat-In-The-Hat) indicating that she's my second wife. And you know, if it were a contest, she wins because we are in fact married.
There are definitely psychological reasons to persist these friendships, not the least of which is that you want to have something from the time you put into it. You shared good times, and were probably there for each other, so unless one of those really toxic things mentioned above were involved, I don't see why you can't continue to be friends even though the romance is gone. It would be hurtful if you couldn't eventually get to that point.
Maybe what bothers me more is that some people can be judgmental about it. That's a statement on a bigger problem though. People get all judgey about a lot of relationships that may be perfectly functional even if you don't understand them (you know, like inter-racial or gay relationships, polygamy, non-marriage partnerships, etc.). I'm sorry if you can't be friends with your ex, but if someone else can, it has nothing to do with you.