IMO, aside from his skills, the biggest improvements in Novak's game are his stamina and maturity.
In the past, he will be seen breathing heavily ang sweating profusely after long rallies. Oftentimes, after an unforced error, he will curse at himself, beat his racquet to the ground or even his head. But now, you can even see him smile at his mistakes and clap at an opponent's passing shot. These are traits that Rafa & Roger learned early in their careers. His time has come.