Just broke up with my girlfriend. What can I do to actually get my mind off her?

We were together for 3 years. She was and still is an amazing person, probably the best person I've ever met. But the relationship wasn't good. Was it due to incompatibility? I don't know. The sex was really good and we had fun every time we were together, but I just knew that it wasn't going to work in the end. I tried, even if it felt like I was a fool sometimes. It was my first actual, long term relationship.

Now that it's over I don't know what to do. The most common advice is "go to the gym", but I go to the gym on a regular basis anyway. Today I made an attempt to go, but I'm barely holding everything in, and as soon as I started working out I felt like I would burst out crying if I pushed myself harder. Like I'm a ticking time bomb, and by pushing myself during the workout, the time that was left would immediately jump to 0.

I love playing videogames, I just beat Splatoon Raiders and Red Dead Redemption 2 a few days ago. However I can't seem to enjoy videogames for the time being, I was planning on starting a playthrough of Batman Arkham Asylum today but I didn't even have the courage to get up and walk to my PC.

I don't have a lot of friends, but I have a few close ones that I hold really close to my heart. We're all adult men though, each one with his own set of problems and issues. I don't want to put this burden on them because I know that if I let myself go, I can talk about this relationship for hours on end. So much wasted potential...

What can I do to get my mind off her? I'm pretty sure that tonight I'll be crying myself to sleep, but at least I don't want to be like that throughout the entire day. Drinking, drugs etc. are off the table, I'd prefer a more "natural" way to stop thinking about her, if that makes any sense.