Matt. 12:33, “Make the tree good, and his fruit will be good.” The root must be dealt with, the nature of the tree changed, or no good fruit will be brought forth.
This is that I aim at: unless a man be regenerate, unless he be a believer, all attempts that he can make for mortification, be they never so specious and promising,—all means he can use, let him follow them with never so much diligence, earnestness, watchfulness, and intention of mind and spirit,—are to no purpose. In vain shall he use many remedies; he shall not be healed.
– John Owen –
from The Mortification of Sin in Believers, volume 6 of Works, page 36