John Owen was a Puritan preacher who understood the nature of sin and the need to be ruthless in our fight against it. Click here to read more quotes from Owen. A few of my favorites are below.
Let no man pretend to fear sin that does not fear temptation also! These two are too closely united to be separated. He does not truly hate the fruit who delights in the root.
Do you mortify? Do you make it your daily work? Be always at it whilst you live; cease not a day from this work; be killing sin or it will be killing you.
Let no man think to kill sin with few, easy, or gentle strokes. He who hath once smitten a serpent, if he follow not on his blow until it be slain, may repent that ever he began the quarrel. And so he who undertakes to deal with sin, and pursues it not constantly to the death.
The vigor and power and comfort of our spiritual life depends on our mortification of deeds of the flesh.