William Wilberforce, Real Christianity

“Let him then, who would be indeed a Christian, watch over his ways and over his heart with unceasing circumspection. Let him endeavour to learn, both from men and books, particularly from the lives of eminent Christians, what methods have been actually found most effectual for the conquest of every particular vice, and for improvement in every branch of holiness. Thus studying his own character, and observing the most secret workings of his own mind, and of our common nature; the knowledge which he will acquire of the human heart in general, and especially of his own, will be of the highest utility, in enabling him to avoid or to guard against the occasions of evil: and it will also tend, above all things, to the growth of humility, and to the maintenance of that sobriety of spirit and tenderness of conscience, which are eminently characteristic of the true Christian.” 
― William Wilberforce, Real Christianity