That’s hard!  I have definitely had those days.  I usually recognize then that I need a change of pace.  I need to work from a different location, I need to go for a walk and think without any internet, I need to sit in a library.  Remove myself from what is eating at me, even just to get something done.  You need to jog your brain back to a place where humour can come out, because you know it’s there.  There is no one who is going to feel funny every day, and that’s ok.