My tip before a fast is to have the last two meals before you start cut out all carbs. That eliminates the glucose crash, shakes, and queasy feeling. Hunger is much lighter if you already are at least partially in ketosis.

Serious intermittent fasters say that you get a burst of energy and feel great after you've been fasting for a while, but in truth, my energy just kept dropping slowly throughout. Like you, the last couple of hours of the 48 or 72 hour fasts I've done has just been a case of watching the clock run down.