Depression is always the worst for me after mania - last time I was having a really hard time, I practiced both GTD (getting things done) which is a self-help/productivity book by david allen that suggests you should take everything and break it into tiny pieces. The other thing I do is I use very finegrained todo lists - found the website Trello works really well I credited it with pulling me out of my last depression. Even if I felt like I hadn't accomplished anything/couldn't do anything, there's boxes to check and things to say "yes I did this" - my recommendation would be to just make some easy boxes to check to give yourself momentum and try to find the things you can do even if you can't concentrate...