MWM,
I understand what you mean.
I have my two lovely younger PCs...I have split custody with their dad, so they are forever coming and going. I love them so much, and they are moving into young adulthood so fast...it is very very sad to see them go when they go, which they do over and over. Sometimes when they've been gone, especially if SO is away, they ask if I've been ok...and I tell them of course, I am practicing for when they are really gone, that that is as it should be. Part of what keeps me from lying down and crying is the need to make it clear to them that this is a healthy good and normal transition and I am proud of them.
Also, watching good movies helps!
I find that other hobbies, like exercise or knitting, leave me too much time in my head. Some time meditating so that you actually grow through the process, and some time being distracted...and of course, letting time just be time, pass, and heal...you will be OK.
Hugs for your aching mommy heart today, MWM.
Echo