In the book "A Clockwork Orange" what motivates Alex to choose to be "good" by excersing his free will?

I think it is his boredom that motivates him, but I need to expand upon that idea. Can YOU help me with this? What motivates him? Thank you very much.

http://www.sparknotes.com/lit/clockworkorange/

http://www.gradesaver.com/classicnotes/titles/clockwork/

I have never read that work, but you might find some information in the sections in these websites on Characters or in the particular part of the story when this change takes place.

=)