Mourn for it if you need.
And move on.
All different kinds of relationships end at all different times and in a million different ways. Sometimes, you're just not useful to each other anymore. Sometimes you're not getting out what you're putting in. That's when the knock-down, drag-out fights happen. Even though you might not want to let them go, maybe its what you have to do. I'm not saying you need to sever all ties and completely cut them out (unless its with an ex-boy/girlfriend... in which case get as far away as possible), but one of the best things I have learned recently is when to let someone fade into the background of your life. That doesn't have to mean letting them go forever; just realize sometimes relationships are cyclical. Maybe they'll have a comeback a few years down the line. Maybe not. But the stress of trying to nurture a fizzling relationship is really heavy. You know its not something you need right now, but you don't like feeling like you're just dumping them for greener pastures.
Its like cooking. You're baking a cake. You need a whole bunch of ingredients. You lay out all the ingredients, and what do you put closest to you and your bowl? The biggest ingredient:: the flour. It doesn't make the sugar or egg any less important, it just positions them at an acceptable distance for the time being. Well sometime later, you're making idk....a quiche... and BAM! The eggs have rotated to the top spot again.
Sometimes things need to be done in the name of self-preservation. And it sucks. But would you be happier always feeling tense and stressed out in your relationships??
And on a moderately unrelated note: my babies graduate todayyyyy!! Wahhhhhh :(