Kaka returned to Milan last month.
"I return to Milan as a stronger player and more experienced after four difficult years personally and professionally," he told Sky Italia.
"In Madrid I learned to suffer the critics, to be challenged and to be constantly under pressure. So many doubts have made me grow.
"The atmosphere at Real Madrid is like that of many other clubs. In Milan, the relationships are closer.
"I face this new experience with a different consciousness to my previous stage. Now I have to exert a role of leader.
"I hope to be in Milan for a long time, to help those who are younger and still learning. Milan 10 years ago was different, but the feelings are the same. It is as if I had never left."