Saint Athanasius the Great

You will not see anyone who is really striving after his advancement who is not given to spiritual reading. And as to him who neglects it, the fact will soon be observed by his progress. 

-- Saint Athanasius the Great

Pope St. Gregory the Great

Perhaps it is not after all so difficult for a man to part with his possessions, but it is certainly most difficult for him to part with himself. To renounce what one has is a minor thing; but to renounce what one is, that is asking a lot.

-- Pope St. Gregory the Great

Saint John of Damascus

God created man to be straightforward, but he has entangled himself with an infinity of questions.

-- Saint John of Damascus