On Not Losing The Capacity for Astonishment in the 3rd Act

A beautiful little piece by Hillman Curtis on Milton Glaser:

http://av.adobe.com/studio/miltonglaser/miltonglaser.html (via Jeffery Zeldman http://www.zeldman.com/)

While I am not entirely inclined towards Glaser's aesthetic, his words hammer right on the bone. What is it about artists that remain vital, astonished, in "the 3rd act"?