IMO what worked well for Rafa was that he doubted himself after being away from competitive tennis for 7 long months. He worked hard on his game to be able to compete at the highest level again.
And he went on to have one of his most dominant seasons. I don't think he planned on that. He exceeded his own expectations winning FO and USO + 5 Masters and other titles.
Once he knew he's back on top, he stopped doubting himself. He knew he was the best player in the world. He stopped doing the things that helped him compete so well in 2013. He practiced, but not like before.
I've said this before. I was very disappointed with him in Miami final. Djokovic was playing very well. But Rafa was just awful. He couldn't or didn't retrieve some balls that even I would have gotten to. He made Novak look even more impressive than he already was.
I thought after that Miami final, Rafa needed to come back strong in the clay swing. He needed to play the kind of tennis that elevated him to the top. But sadly, he didn't, and got bounced by Ferrer in Monaco. A few days later he loses to Almagro in Barcelona!
The way I see it, Rafa will have to fight hard and play his best to be the dominant king of clay again. His B game is no longer good enough against quality opponents. He isn't getting any younger or faster. He's gonna have to be near his best to defend his FO title.