Let's say there is a desirable and attainable and even archetypal psychological arc to life.  One running parallel to the ignorance to knowledge to wisdom arc. 

Does it flow from uninformed, giggly bliss to brave gravity?  Or does it flow from frustrated suffering to smiling, enlightened invincibility?

I think Steinbeck chooses the latter:

She went back to work.  "Do you think it's funny to be so serious when I'm not even out of high school?" she asked.

"I don't see how it could be any other way," said Lee.  "Laughter comes later, like wisdom teeth, and laughter at yourself comes last of all in a mad race with death, and sometimes it isn't in time."

I support that choice.