Break-ups can be hard and we do many things to get over them. But there's a few things most of us tend to forget in the process.
A long term relationship for better or for worse forges your identity in a different direction. When you break-up this identity of yours is now reshaped/destroyed/collapsed/etc. Healing from a break-up doesn't work when you just focus on yourself.
Think of it this way. You had an amazing structure you built from Lego and it crashed and tore apart and you've lost some of the pieces. Now the structure might have been unsound, someone/you/them might have destroyed it even though it was fine, there are many possible reasons for its collapse. Now in most cases these pieces are missing that you can't rebuild the same structure anymore. You might have a lot of skills and abilities that function as blocks in your box or you might need to go and acquire some. But what you build will be something new, something different. It won't be the same thing. Don't assume when you rebuild you are rebuilding the same thing. You aren't going to feel the same thing. You can feel a lot better possibly but it requires you to have the focus to build something new and amazing.
For that process you need to go out and plan out what you want to do with the next few years of your life. Build that identity again, shape it, own it. Expose your emotions, remember all the things from the past but remember that you built this and you can build something again. Your identity will resurface to before you were ever in relationships, your happy place in a way. Your new identity will form and it has so much propensity to be better, to be amazing. But in order to do that you need to mourn the loss of the prexisting identity. It needs a burial/funeral and so you can come out of it again. Just focusing on building something new without taking care of the old means no matter how many skills you acquire, no matter how much you hit the gym, no matter what you do - you are still carrying the rotting corpse of your old identity with you and as time goes by this can stink. Many of us manage to throw it away but some of us become one with the corpse and some of us just attach bits of that corpse to ourselves for comfort. Mourn your old identity, discard the corpse and build anew.