Originally posted by Phil:
Glad you liked it, Tuck. I've enjoyed reading Kreeft, and his remarks at the end of the article on sex in heaven are a real turn-on!

I've understood "becoming as a little child" to refer to how unassuming children are, and how open to the moment in wonder. They're also quick to forgive and open to love and loving. So we're called to be child-like in this sense, but not child-ish.
In Jung's psychology, the child is a symbol of the deep inner self, so it could be that Jesus is also referring to this aspect as well.