John Owen wrote, "Men are not so vain as to hope for skill and understanding in the mystery of a secular art or trade, without diligent use of those means whereby it may be attained. And shall we suppose that we may be furnished with spiritual skill and wisdom in this sacred mystery, without diligence in the use of the means appointed by God for the attaining of it?"
Let me say this in another way. Men are not so foolish as to think that skill as a surgeon or a concert pianist can be gotten in dribs and drabs at one's leisure. It takes thousands of hours of applied effort in study, practice, and experience. How can we be so foolish as to think that skill and wisdom in godly living or a profound understanding of God's holy word can accomplished with less devotion?