It's not just his mental aggressiveness that is the factor, he has to play more attacking tennis on hardcourts (and grass).
he's actually quite good at the net and during his final at Doha he was coming forward much more often after Davydenko showed some weakness in the 2nd set. If this becomes more of a habit/tactic it will really trouble his opponents.
Disclaimer: I'm NOT a coach...
Real tennis: https://www.youtube.com/watch?v=yDqnkLJ9BtM