I've now simply decided to look pain in the eye and embrace it. It is inevitable and important in forming relationships. At least you have mostly fond memories to look back on at the end of it.
This is the worst bit for me. I've never been able to look back without extreme pain. I always wish I did or said something different. Or just that I had more time or was more appreciative in the moment.
Trying to live in the moment works better for me. I try to make the most of now and keep change to a minimum so there's not too much to worry about losing and there isn't too much to miss.
I think your approach is more healthy, I just don't seem to be able to do it. I think it's something to with ASD. I seem to get very attached to people, animals, places and times. I hate change, especially when it's preeminent and out of my control.