185 Take care then, Venerable Brethren, that this true and solid piety increases daily and more under your guidance and bears more abundant fruit. Above all, do not cease to inculcate into the minds of all that progress in the Christian life does not consist in the multiplicity and variety of prayers and exercises of piety, but rather in their helpfulness towards spiritual progress of the faithful and constant growth of the Church universal. For the eternal Father "chose us in Him [Christ] before the foundation of the world that we should be holy and unspotted in His sight." All our prayers, then, and all our religious practices should aim at directing our spiritual energies towards attaining this most noble and lofty end.
Source: Mediator Dei (Vatican.va)