FriENDships and BoyFriENDS (or GirlfriENDs).....
The "end" is a relevant and natural part of life. To some it may be a sad reality, but that is just what it is...reality. Many friendships (or few) that you have will come to end and the same goes for boyfriends (or girlfriends). They end for a variety of reasons but the similarity is that they END.

My view on this subject is that life goes on. Now don't get me wrong, of course it may hurt for some cases, seeing that we have emotionally invested in these people, shared our thoughts, beliefs and lives with them. However, I do not think it is necessary to be mourning the loss of these people from our lives for years.-__-. They are not dead, though sometimes...never mind. Back to my point, I never saw the big deal people who are not involved in the relationship (the one that is ending) make over the end of said relationship. It is not the end of the world, chill out. These people came into our lives and are now leaving our lives, and trust me, there are plenty more of these cases to come. It is a unavoidable part of life, unless you decide to become a recluse and then all you have to worry about is whether your fave tree might get chopped down some day :/.
The fact is people grow, start liking new things, drift away, start developing different views of the world, go into different directions in their lives and so, this causes tensions and problems which have reached beyond the point of being resolved and so, decided, sometimes unanimously or not, to go their separate ways.
My advice is to try and find the lesson that this person has taught you from being in your life no matter how large or insignificant the lesson(s) was. Learn and grow from the lesson, then move on with life. The main aim is to be happy. No use crying over spilt milk, or so they say. I'm sure when some of these relationships ended it was like a weight was lifted off your shoulders \o/. I know personally, this has been the case for most of the relationships that have ended in my life. Maybe that is because I did most if not all of the ending :/.
Anyhow, if someone no longer has a positive impact in your life or is constantly making you sad, depressed, and yada yada, do not prolong it, cut the cord and move on. You only get one life, unless you're Hindu or Buddhist, so enjoy it while you can. Happiness is not a destination or end point, it is a journey and on going process.