Usually when you are watching a tennis match even when you do not know the score of the match you can tell who is dominating at the moment by looking at the body language, usually ... but not when it is Nadal playing on one side.
Nadal seems to play with the same exhuberance no matter where he is at, the best example would be Nadal playing the 2nd set in the 2006 Wimbledon final( He had lost the 1st set to Federer 6-0 !)
Having played numerous tennis matches in the last 2 years( V and I actually played our first match USTA try out match on 31st Dec 2005); I have realised when you lose a set or a game and not lose your go get attitude, it sort of unnerves the opponent. Sometimes riding on that wave it even brings your confidence back, your belief back, it puts you back right into the game!
I am happy to say that this never say die attitude has won us many a match, brought us back from the brink of defeat to victory, sometimes we lose too but.... oh well it is the journey that matters not always the destination ... a match hard fought and lost is much better not having put up a fight and lost!