I was quite struck by these words of John Calvin on the nature of true repentance:
"It is a most difficult and arduous achievement to renounce ourselves, and lay aside our natural disposition. For the flesh must not be thought to be destroyed unless every thing that we have of our own is abolished. But seeing that all the desires of the flesh are enmity against God (Rom. 8:7), the first step to the obedience of his law is the renouncement of our own nature.- John Calvin, Institutes of the Christian Religion, III.III.8
...As we are naturally averse to God, unless self-denial precede, we shall never tend to that which is right. Hence we are so often enjoined to put off the old man, to renounce the world and the flesh, to forsake our lusts, and be renewed in the spirit of our mind. Moreover, the very name mortification reminds us how difficult it is to forget our former nature, because we hence infer that we cannot be trained to the fear of God, and learn the first principles of piety, unless we are violently smitten with the sword of the Spirit and annihilated, as if God were declaring, that to be ranked among his sons there must be a destruction of our ordinary nature."
The Death of Athaliah - Gustave Dore