"Maturity" is the balanced, stable and content ego-mind of later life. It precipitates once the many worldly skills have been learnt and integrated so as to operate automatically. The mature can be said to "have their act together" - an apt expression, as it is truly only an act which they have perfected. They are actors, who after long years of practice have perfected a certain role. And they are ever comfortable with that role, provided the stage is set for them.
The more composed, or balanced a person is, the more secure is their ego, and the less likely they are to partake of any real thought. They will not risk everything they have built up during their life, not now. They believe suffering is behind them. "Suffering and anxiety are for youth" they think in their deepest thoughts. "We need hardship to mature" they reflect. Oh Great Wisdom!
The mature man is one who has lost the strength and desire for perfection, and now proclaims such striving to be folly. Here begins compassion . . .