It's workouts like these that remind you just how important your pre-workout nutrition is. If you've been following the program, you should have enough carbs and protein in your body for extended energy.
Yes, this workout is supposed to be difficult, but if you're seriously dragging ass, it probably has a lot to do with what you've been eating. The goal of this program is to build muscle, so if you're trying do this workout in a calorie deficit, you're just asking for trouble.
Today's taxing leg session calls for giant sets, supersets, and intraset stretching . Remember to rest as little as possible between exercises during your giant sets and supersets. Push yourself to the limits, and then enjoy your rest periods after these grueling sets. Your extreme efforts will lead to maximum growth.