Never the same ending twice

I was talking with Lisa last night about what to do in a friendship that appears to be coming to an end. See I don't do endings well. I don't expect relationships to end so therefore I don't know how to wind them up when they do. I've been through friendships that have ended before, but no two are ever the same, so I can't take what I've learned from those and apply it to the current one. I've had ones that changed due to the pull of time and distance. I've had ones end because of the mistakes I've made. I've had the short lived ones that were for a season or for a particular reason. Lots of different kinds of friendship, but none that I ever went into thinking there was an end coming. When I become friends with someone I just don't expect it to end. Naive? Probably. Unrealistic? Probably. But I just can't see the exit strategy. I don't see it stalling and failing to grow. I don't see the change of personalities coming. It comes as a surprise to me any time it has happened (may be that I am just a really, really slow learner.) So here I am and sense it happening again. A change coming. We are walking away and I'm not sure how to end it. Oh, they probably don't see it as ending. Just life and circumstances changing. Things happen and you move on. I just have trouble with the moving on because that says it is over. I'm not ready to give up, but that doesn't change where I am at. How do you end a friendship that you have invested yourself in? How do end something that is part of you? How do you stop caring? How does it end?