The first thing is to pack things between you two. When a person is very uncomfortable, it is actually a very pleasant thing to pack things, because in the process of packing, you have been sorting out your mood. Maybe at that time, after you have cleaned up all the things you remember between the two of you, you may not feel so bad as before. Because after all, as the saying goes, when you put away the memories between the two of you, there is nothing worth remembering to connect with your past and remind you of the life of the two of you together in the past.
Second, if you still feel uncomfortable, you can go outside and see the scenery outside. Travel alone and let yourself see the outside world instead of being confined to your own small world. Because you have to know that after you have seen more scenery and met more people during your trip, you will understand that everything in the past is nothing, and the future is the most important thing.
The last one is that you must understand one thing. You two broke up and he decided to start a new life. Are you the only one left in your previous memory? It's not fair to yourself. Why can he start a new life? Why can't you?