Hardest day for P90X

I'm not really sure why this workout was so difficult. I did the "Legs and Back" workout last evening. I don't think I've sweat so much in my life, I was dripping. My legs were literally failing, I was stumbling and falling occasionally. It was beyond rough. The workout has plenty of squats and lunges using handweights. The wall sits were unbelieveably hard last night, the first round was just two leg wall sits for 1 minute 30 seconds. The second round is one-leg wall sits. If you've never tried doing this, give it a shot for a good laugh. You have to do it for 1 minute alternating legs every 10 seconds. I barely made it through. It's complemented by 6 sessions of different form pullups.

I've done this workout a handfull of times already, but last night was THE HARDEST workout of this program by far. I wanted to give up so many times. I finished the 1 hour leg and back workout and also completed the 15 minute ab workout afterward. I think it was a combination of me being tired from swim practice and it was at the end of a very long day. I slept like a rock after that workout!