dont know where to go from here

my ex (21m) broke up with me out of nowhere, he had been struggling with mental health issues and managing life and couldn’t handle a relationship right now. We had been together over 10 months and it was a healthy relationship and he was a wonderful boyfriend. We were best friends and share all the same friends and the same major. I really want to fix this but also respect his need for space, he reached out after a month of NC to try to explain the break up and see how I was. I told him I was good but couldn’t handle being friends and that he knew my number and that I was always there for him. Since then its been almost another week of NC and we went home to separate states for break. I have belongings of his here that I need to send back, maybe wwith a letter saying “thank you for sharing so many wonderful things with me, I hope youre doing well. Happy Holidays.” Does anyone have any ideas for how to rebuild something here? Thank you