51 But let Us repeat once again for our common admonition and profit: the Church will rediscover its youthful vitality not so much by changing its external legislation, as by submitting to the obedience of Christ and observing the laws which the Church lays upon itself with the intention of following in Christ's footsteps. Herein lies the secret of the Church's renewal, its metanoia , to use the Greek term, its practice of perfection.
Source: Ecclesiam Suam (Vatican.va)