Pope John XXIII
Sacerdotii Nostri Primordia §36
Prayer in the Life of St. John Vianney
36 How timely and how profitable this example of constant prayer on the part of a man completely dedicated to caring for the needs of souls is for priests in Our own day, who are likely to attribute too much to the effectiveness of external activity and stand ready and eager to immerse themselves in the hustle and bustle of the ministry, to their own spiritual detriment!
Source: Sacerdotii Nostri Primordia (Vatican.va)