Probably thinking in the 1st Set that he should do his best and prove how good he is, then fade in the 2nd Set probably feeling "bored" seeing that there is no challenge, then wakes up in the 3rd realizing how much trouble he is in. I think he needs to control himself in these situations, to reserve energy when needed so he wouldn't be wasted mentally to be vulnerable. He should think that there is more to the tour than just winning a Slam because if that was just his drive (already reaching the top of the game) then he should re-evalute himself IMO. Oh well...I just hope this was enough (plus his IW loss) be alert consistently for the next match -- I think he is just not yet fully ready to be "big".
Yeah I hope he finds the motivation. This is why Magnus plays a big role in that, he needs to help him realize that it's not only about Slams, and that your tennis career is not finished once you get one Slam. If he thinks that way he may just as well retire.