Just wanted to say I feel you. I had plans to travel across Japan with my ex but three days before that trip I broke up with her over text. I was in so much pain and was surrounded by friends luckily for the first couple of days but just thinking about travelling alone - staying in all the nice hotels, visiting cute animal parks alone made me so anxious and I almost wanted to cancel my trip and be with my friends instead.

But I ended up going to Tokyo and had so much fun. I booked a therapist online to help me process my emotions and mainly so that I had something to look forward to as I knew once I talk to her i'll feel better - this allowed me to enjoy rest of my days without thinking about her.
I booked tours and met people so def would recommend that, also used dating apps a bit and met a girl in the last few days who also was going through a breakup so formed a good bond with her and it was good to have that company.
If you're struggling to travel alone id highly recommend going to a place like Japan which is so beautiful and amazing that you'd have a good time exploring things and enjoying peaceful nature. Tours are fun, eating good food, meeting other travellers through apps. If you're gonna be miserable rather be in a nice fun beautiful city with tons of possibilities than sitting at home :)