It is just as shameful for lovers of the flesh and the belly to search out spiritual things as it is for a harlot to discourse on chastity. A body suffering grave illness shuns fatty foods and abhors them; and likewise, a mind occupied with worldly affairs cannot approach the inquiry into the things of God. A fire cannot be ignited in wet wood, nor can the divine fervor be kindled in the heart that loves ease.

St. Isaac the Syrian
Ascetical Homilies (Homily Four)