I think he was an emotional wreck, from watching "This is it". If you compared that to any other footage of MJ rehearsing, he looked more happier and energetic during other rehearsals. Michael looked tired and irritated. I mean, he was 35 % Michael Jackson in "This is it". Usually, Michael Jackson is a speedy person when it comes to dancing, and he's always sure. In that movie, he looked a little confused, at times, and kinda down. The movie "This is it" was greatly edited to show us a few of the good parts of his rehearsals.
Look at this:
http://www.youtube.com/watch?v=rH9j761YgNM
He was a beast.