What Was Young Roger Federer's Weakness?

David Senra, reading Christopher Clarey's The Master, says an undeniable weakness in Roger Federer's early years was his mentality. Federer was a terrible loser, and his self-control was lacking. He knew what he could do, and failure made him mad. He had two voices inside him, the devil and the angel, and one self could not believe how stupid the other one could be. One voice would ask how he could miss that, and then he would explode.

His dad used to be so embarrassed at tournaments that he would shout from the side of the court, telling him to be quiet. On the way home, his dad might drive for an hour and a half and not say a word. Federer's lack of mental discipline was the biggest reason he was not a can't-miss prospect. He clearly had the talent and seemed to have the ambition, but the mental game is often what makes the difference between mediocre and good, and between good and great.