I have concentration problems. "Concentration problems" is a bit vague but specifically I struggle with:
1) Easily distracted (by things that are 'easier' to do like surfing the Internet).
2) Unable to logically figure things out. I can see there's a problem with something, and have some idea of how to fix it, but can't figure out how to get from A to B. Even for pretty basic problems. I really don't have a solution for this.
3) Complete lack of motivation/willpower. (I just don't see the point/I don't care/I give up easily.)
4) Inability to focus because I have too many other things on my mind.
As a result, I cannot read anything remotely difficult, and it's pretty much impossible for me to find solutions to complex problems. I also struggle with expressing myself, and difficulty telling if I'm being clear and precise.
This issues affect me more at my job than with my writing, I think. At least, I am less worried about how they might affect my writing.
I try to put myself in a better frame of mind by going for a walk or something like that, usually with limited results. On really bad days, I try not to push myself, (but that doesn't work so well when it comes to my job). Also, if I'm really stuck, I let myself move on to something else. No point beating myself up over it. Overcoming #3 to some extent helps me move on to dealing with the others, but it drains me to force myself to be motivated day after day when I'm really not.