To me, focus is one of the casualties of a relationship with an A.
When I go to my Al-Anon meetings and hear "taking the focus of them and put it on you", it helps to get me out of that red zone where I would think of a)whether they were sober, b) whether they were drinking, c) whether they were about to drink.
Now that the A is out of my life (close to three weeks now), I find that I can focus a lot easier (not perfectly) on things I have neglected or need to be done, like homework. Never had the support from my A when it came to my courses and my last assignment (post breakup), I got 100%. Another thing-I can sit down with a book, enjoy it, concentrate on it totally, not waiting for the phone to ring or the next crisis to unfold.
For me, walking my dog is a big help to re-focus, as is sitting out in my back yard with a book - no phone, no music, just the quietness of the neighbourhood and my beautiful view.