I don't think that I'm unique in this experience (I've spoken with others that have the same experience), but have you ever solved some of your most difficult problems in your sleep?  It happens repetitively to me.  Time after time, especially after slaving away and not getting anywhere on an issue (primarily code issues) I solve the problem in the middle of the night while I'm sleeping.  I hate it when I wake up, fully aware that the problem was solved, but am unable to recall the solution - it's infuriating!

Case in point: I am working with a friend from California on an ASP.NET product and am banging my head against some pretty intense issues.  Just the other night I was (while sleeping) running into the issue yet again, but solved it rapidly.  When I awoke shortly thereafter I knew the problem had been solved but couldn't remember.  But this morning while working on it came to solve the problem and had a deja vú moments and the dream came back to me.

Maybe that's why I like to sleep as much as I do.  Or perhaps it's my body telling me that it's time to solve problems and it wants to shut down.  I guess I should listen to it more often rather than kill myself working into the wee hours of the morning.