Children

child·ish 
1: of, relating to, or befitting a child or childhood2 a: marked by or suggestive of immaturity and lack of poise childish spiteful remark> b: lacking complexity 
— child·ish·ness noun
VS 
child·like
: resembling, suggesting, or appropriate to a child or childhood ; especially : marked by innocence, trust, and ingenuousness
— child·like·ness noun

God calls us to be like a child, not childish (Matthew 18). I think the most fitting synonym for childishness is selfishness. My prayer for 2009 is for more of the world to stop being so selfish and grow up.