My experience with the above has been this. Generally I get a good nights sleep--though if I eat excessive carbs at lunch I am fighting the fatigues, so I don't do that--when the client's call me on nodding off--which has embarrisingly happened more than once it jolts you right out of what ever fatigue you were in. I always let them know that it isn't them, even if it is the same story--I have either a cup of coffee or soda late in the morning and that pulls me through the rest of the day.
Beth