Do we ever "grow up"?

Back when I was in high school, there was a history teacher who hit it on the head. Maturity is not about being mature all the time, it's about knowing when to be immature.

"We do not grow absolutely, chronologically. We grow sometimes in one dimension, and not in another; unevenly. We grow partially. We are relative. We are mature in one realm, childish in another. The past, present, and future mingle and pull us backward, forward, or fix us in the present. We are made up of layers, cells, constellations." Anais Nin