Welcome to PC. Everyone that has posted already has given great suggestions, so I am going to say "ditto" and give you hugs, if that is ok.

For me, what helps, when my kids do something silly/sweet, I try to hold on to how that makes me feel and then when I am really down, I replay that in my head. Sometimes it works, sometimes it doesn't. (even videotaped on my fone my daughter doing a goofy 'can't touch this' dance and it cracks me up)

Sending hopeful thoughts your way...