The former Fiorentina star has shone for Juve this season.
"Juve make you grow, but only if you're able to receive the messages they send you," he told Gazzetta dello Sport.
“Now I'm a man and a complete player, but I'm not stopping here. At the age of 16 I didn't grow physically, my teammates were men and I was still a boy.
“It was the most difficult phase of my career, but it was there I learned that every day you suffer to reach a small objective.
“However, when you succeed, you must enjoy it before raising the bar again. A leader must be intelligent, conscious, mentally strong and set an example every day.
“This season I've made a leap in quality, of which I'm very proud. They're processes of life, moments of growth and maturation: it's there when you really change."