The following is from a letter by John Newton.
"Were I to define a Christian, or rather to describe him at large, I know of no text I would choose, sooner than Galatians 5:17, "For the flesh lusteth against the Spirit, and the Spirit against the flesh: and these are contrary the one to the other: so that ye cannot do the things that ye would."
A Christian has noble aims--which distinguish him from the bulk of mankind. His leading principles, motives, and desires--are all supernatural and divine. Could he do as he desires--there is not a angel before the Eternal Throne, that would excel him in holiness, love, and obedience! He would tread in the very footsteps of his Savior, fill up every moment of time in His service, and employ every breath in His praise!
This he would do--but, alas! he cannot! Against these spiritual desires, there is a contrary desire and working of a corrupt nature, which meets him at every turn! He has a beautiful copy set before him in the Scriptures--he is enamored with it, and though he does not expect to equal it, he writes carefully after it, and longs to attain to the nearest possible imitation. But indwelling sin and Satan continually jog his hand, and spoil his strokes!
Therefore, the most spiritual and gracious people confess themselves as vile and worthless! One eminent branch of our holiness, is a sense of shame and humiliation for those evils which are only known to ourselves, and to Him who searches our hearts!
In proportion as the Lord enables you to live more simply upon the blood, righteousness, and grace of the Mediator--you will possess a more stable peace. The nearer you are brought to Him--the more lively sense you will have of your vileness and worthlessness; and your continual need of Him. Thereby your admiration of His power, love, and compassion, will increase from year to year."