To discover the will of God is both a simple and a complicated matter, both clear and obscure, both sad and joyful, both ordinary and extraordinary, depending on the individual case. Therefore, neither a casual attitude nor exasperation, nor tormented uncertainty is called for. But prudence, examen, prayer, counsel, and decisions in faith.
Where there is innocence and the right environment, the divine voice often manifests itself soon after the age of reason (i.e. seven years old -- Rae).