i think people often react to, or deal with, the ending of relationships differently. some people probably do see endings as more natural, or conducive to new beginnings and growth. there are also relationships that are a pain in the butt, or just not very exciting, so when they end you don't feel much of anything but relief. i've had that at least once. i cared about the person when they were around, or thought i did, but when they were gone i really never gave them much of a second thought, and i certainly never wished they were back. sorry. heartless i know. but true.
however, there are those of us - and this includes me in most cases - who find endings almost unbearably painful and will continue to do so. it will never be a positive experience. it will never be "growth". at best, it will get numb, so when you get reminded of the person or worse yet have to see them around on a regular basis you'll be able to just not feel much of anything so you can say "hi" like a normal person without wanting to hide under the table, or puke on the floor, or scream and yell and punch.
i'm pointing this out as a public service announcement. if people still honestly feel that their own endings were healthy and growthful things, or grew to be that way later, that's fine for them i guess. just don't expect the whole rest of the world to share your happy pills. and i don't think "letting go of grudges" in the sense of forcing yourself to feel some sort of forgiving way you don't or can't, because you're not MADE to be that way, or else you wouldn't be able to love and commit so strongly when you DO decide to - I don't think that kind of "letting go" is healthy. Sure you should "let go" in the sense that you have to get comfortably numb after a while, you can't let it run your life, you can't keep boring yourself or your friends, you have to get on with things, you may even get so involved with other people and activities that you become much happier and FORGET about it even for short periods of time. But you don't have to pretend it's all happy-dappy when it's not.
Some things will never be happy-dappy. Some things just suck. Some things will always suck.
And that's OK.