I believe that there should be a balance between maturity and immaturity; know when be serious and when to be silly.
Also, I think it shows real quality in someone when they can look beyond age, appearance, race, etc. and see a person for who they are (not what they are!), accept them even if they don't particularly agree with/like/tolerate them and not dwell upon wasteful emotions, such as "hatred". Lol, there should be more love in the world ;D