That's as valid a reason as any -- I clicked on your link and saw that you are quitting smoking. That will affect your performance and any ex-smoker will understand and empathize. I know you know already, but it does get better with time -- your concentration and focus will come back, maybe in a slightly different way.

I'm so sorry you're dealing with this now. It sounds very stressful and that's not the way to start the summer! I hope you get some time lying on that mattress or on a lounge chair in the sun.