I think every man almost entertains this secret persuasion in his breast, – that his nature may be weak, yet it is not wicked; it may be helped with education, and care, and diligence, and dressed till it please God, and profit others. Who is persuaded in heart that he is an enemy to God, and cannot be subject to God’s law? Who believes that his “heart is desperately wicked?” Oh! it is indeed “deceitful above all things;” and in this most deceitful, that it persuades you ye have a good heart to God.
Source: http://www.puritanboard.com/showthread.php/89055-Deceitful-above-all-things, Comment 1