Maturity isn't acquired necessarily with age. We can be advanced in years and still think and behave immaturely.
Maturity comes with understanding Life, having a relationship with It (God), and through this relationship know ourselves. Being honest with ourselves is primary, as we look within with non-judgmental yet clear vision, so we can let go of beliefs and thoughts that keep us in fear.
As I deepen my faith and relationship with the Divine, I find that I trust more, am more at ease and let go of the need to control. I am also less "reactive" to life's challenges because I know I'm loved and cared for.
This maturity comes with knowing myself through the eyes of God.
As I willing choose to see others through this Vision, the sense of separation, the resentments and unforgiveness I hold in my heart begin to give way to oneness, true forgiveness, and ultimately love.