In need of inspiration

I'm officially single for a couple of weeks now from a selfish person who didn't appreciate me. Although I know this in my mind my heart is still very much with him still. I'm a leo and I've been told I'm very strong and bounce back pretty quickly, however that grieving period is HORRIBLE time for me. I miss him even though the right thing to do is walk away. The idle mind is a terrible thing. All I do is think about the what ifs and feeling like he's moved on and I'm sitting here unhappy and lonely.

I'm a loner for the most part. I have friends but more associates than friends and sometimes it's hard to talk to ppl about your feelings because some don't understand or many don't care and I get that. I keep most to myself. I swing back and forth between anger and hurt and then crying. Once I'm past it I know I'll be fine, but this is the hardest for me because I thought marriage was gonna come from this and he was my best friend despite all the bad he's done. I put so much into this relationship than any other and all for nothing.

As a leo who has bee in love how did you get over that one because it doesn't seem to be getting better for me.