According to Osho, maturity is the relaxed acceptance of existence as it is—dropping desire, ambition, and the urge to become. It is the part harmonizing with the whole, seeing there is nothing to reach because you already are, and discovering no-self. From this insight, effort turns into play, the future stops disturbing the present, and suffering ceases.
Maturity means stopping the chase to become someone and peacefully being as you are, in tune with everything.