I have fallen asleep while praying. I used to fall asleep while reading the Bible. The problem in the early years was that I had bought a large NASB and each time I feel asleep reading the Bible I would get a sore nose. How do we stay awake when we have to confess “the spirit is willing but the flesh is weak”? One way I found in the past to beat this problem was rather than set a certain time for praying which most often happens at the end of a busy day, let God set the time. In other words just say to the Lord, “Lord, I am not going to set the alarm. Rather You wake me when I need to wake. Then trust Him to do it. But that is dangerous too I can tell you. There will be times when you will be allowed to sleep in. Learn not worry about it. But there will be times when He wakes you at inconvenient moments; when you don’t want to get up and pray. However breaking through the comfort barrier is a guarantee of blessing to come. But we need impetus to be able to overcome our lethargy or indolence or inertness or something.