mum- I am so sorry you're hurting.
I'm currently going through a divorce and I cry a lot but I've realized it isn't for marriage/family life we had, I cry for the marriage/family life I envisioned that will never come to be. For me, I continue to mourn the disappointment of a dream that will forever be unfulfilled.
After I'm done crying so hard there is nothing left to cry - I do my very best to realize that if I stayed, my dream would have NEVER had the possibility to become a reality. I find comfort in my hope that by leaving, there is a possibility for me to find it with someone else.
Also - my STBXAH moved half way across the country already! It's not easy but we're strong and remember you're not alone.
Sending you lots of hugs and support!