The fog is finally lifting - it gets better each time I get a full night of sleep. I've been surviving by concentrating on one thing at a time, writing everything down if I want to remember it, and adding a multivitamin. Taking long walks has been helping me even out. It's been essential for me to concentrate on the task at hand and not get upset by everything I have to do in the future. Also, if I'm trying to write an email, and I can't make it coherent, I just leave it as a draft and come back to it later, instead of getting upset.

Thanks for the help everyone! You've made brain fog a manageable problem.