Well... in my case I normally use the mornings to attend to and carry out my daily tasks and duties... and play poker in the afternoons and nights according to the time I have...
I live in Ukraine. Most tournaments for me start in the evening. Also, in the poker rooms where I play, the peak of the number of players is in the evening.
Why not all day and night. You just gotta know when your losing your wits and go play some lower stakes tourneys. If your sleep deprived just play ABC poker on some mirco stakes games.