First of all, don't give up. What you are going through is not what you deserve, but a transition to the next stage in your life. Just because a relationship with someone didn't work out as you had hoped for does not mean you can't have even better relationships with others in the future. Adjustment takes time, so don't be judgmental about yourself. (Unsolicited advice, I know. I am about to get separated after a 20-year relationship myself, so I may be writing this in part also to myself.)

Now may be the time to learn who you really are! Do you have any interests you never really pursued because of lack of time? Are there any things you once planned to do but never really found them important enough to prioritize against being with your SO? You may need to think back several years to discover those... How about reconnecting with friends you may not have met only infrequently during recent years? While previously your schedule might have been defined by others in your life, now you need to take active control of it.

One thing that works really well for me is social dancing. It feels like a tactile game where the goal is to have fun and express what we hear in the music through connected movements. When I get to dance with a partner who's really good, it feels almost euphoric. It can be very-very rewarding. And there is most likely a community of social dancers who you can connect to. There is a bit of a learning curve, but there are dances like Cuban salsa where it is not so steep.

Good luck!

EDIT: added one more thought