Practice when your mind is focused and in good mood , probably 2 hours after you woke up...because your mind is still in the ALPHA state, the period where the mind is in the most clear receptive state, Its still fresh and not yet saturated with other concerns.

You will find out, its more productive if you practice this way even for 2 hours rather than practicing 5 hours without focus..trust me in this, It really works.. ;)