In a talk given at Brigham Young University in 1996, F. Enzio Busche quoted a writing of Johannes Cassian about tired saints:
It is easier for a worldly person to come to a healing change of his life, or even to the top of perfection, than a tired saint who is fallen from his first enthusiasm, because the worldly man will go through pain and agony and, sooner or later, he will not be able to stand it any longer, and will rush in the depths of depression to the source of true cleansing. But, when somebody has begun to pollute his name as a saint, without joyfulness and enthusiasm, he will still feel safe and, therefore, will not recognize what he is missing and, therefore, he is not easy to be taught. He will say in his heart, I’m blessed. I know it all and need nobody. [Johannes Cassian, Spannkraft der Seele (Freiburg: Herder, 1981), pp. 14950; or see John Cassian, Collations (Conferences) 4:19].1
Cassian was a religious theologian and lived ca. 360 to 435. He founded the Abbey of St. Victor, a monastic foundation in Marseille in the south of France.