What does being mature and not a child, have to do with love being patient and kind, with love not being jealous, rude or self-serving?  A child needs to learn to be patient and kind, not to be jealous, and so on.  Some, sadly, never learn these lessons and remain spiritually immature.  There are times we can all display elements of spiritually immaturity, after all, love is patient; patience can be difficult.  It is something we want everyone else to have with us while we are free to limit the patience we afford them!  Love is kind, not selfish.  Jesus was love incarnate, and the Kind-One says to us Come, take up your cross and follow me.  He was not limiting us to just accepting our struggles in life; He was challenging us to deal with them as He dealt with them and always with complete kindness, charity and mercy.  He invites us, He wants us, to achieve spiritually maturity.  We all have some spiritual growing-up to do in order to live truly Christian lives.  Achieving this is a goal of our earthly pilgrimage and we only achieve it by imitating the Lord who is always patient and kind, loving and merciful.

…but now I put aside childish things.