Hey @PyrrhaMortimer
Ever heard the saying if you love someone set them free? I honestly think this is what you need to do, I understand that breakups are hard but if it's meant to be it will work itself out in due time. I have friends who broke up with their boyfriends only for them to get back together down the track and are now married. It helped them to grow as individuals and realise just how much the other person meant to them.
It takes two to have a relationship and I get the idea/image that he doesn't want to be in a relationship at the moment and you have to respect his decisions. You can want to fix things and make things work but if he isn't willing to put in any work then its not going to move forward or work out and you will start to resent him for it. While he can still do career stuff in a relationship, in his mind its one or the other and he has (unfortunately) chosen the career for the moment.
There is also NOTHING wrong with missing him and mourning for the relationship that once was but now is also the time to try new things and take chances. Being single is great, you can do whatever you want and not have to worry about another person. You can watch whatever movies and tv shows you want and there is no one judging you for eating half a tub of ice cream. Why not try focusing on you and dating yourself? Go see a movie alone, do some shopping, have a nice long bubble bath, read a good book or binge that Netflix series you have been eyeing off. Just do whatever you want to do, and be selfish for once 🙂