I've been in NC with my ex for some time now (not too long, I haven't been counting, but its not more than a couple of weeks). Her birthday is coming up, and I'm starting to miss her. I've been depressed, but I didn't want her back, but now, the dull depressive like state is starting to be replaced by agony. I'm in a bad, painful place.
I'm sure everyone here can relate to what you are saying here - I certainly do.
When I find myself slipping back into that negative 'head-space' I get real busy - fill my life with positive & joyful experiences &
get the good hormones flowing through my body. Kind of like tricking our bodies into a healthy physical/emotional state ... . tricking is not such a good word but I'm sure you know what I'm trying to say here ... .
Spend time with quality people sharing a few laughs along the way, watch some comedy, help and old lady across the road being rewarded with genuine appreciation and a smile, work, redecorate your house, a new hobby, anything and everything positive. Get the good hormones flowing (joy, laughter, make a big list here). Drive out the bad thoughts with good thoughts. Make a list and get real busy - go for it... .