Not All Weakness Is Sin

John Newton, July 1764 letter: 

It is common to overcharge ourselves. Indeed, we cannot think ourselves worse than we really are; yet some things which abate the comfort and alacrity of our Christian profession are rather impediments than properly sinful, and will not be imputed to us by him who knows our frame, and remembers that we are but dust.

Thus, to have an inform memory, to be subject to disordered, irregular, or low spirits, are faults of the constitution, in which the will has no share, though they are all burdensome and oppressive, and sometimes needlessly so by our charging ourselves with guilt on their account. The same may be observed of the unspeakable and fierce suggestions of Satan, with which some persons are pestered, but which shall be laid to him from whom they proceed, and not to them that are troubled and terrified, because they are forced to feel them.

Lastly, it is by the experience of these weaknesses within ourselves, and by feeling our utter insufficiency, either to perform duty, or to withstand our enemies, that the Lord takes occasion to show us the sufficiency, the freeness, the unchangeableness of his power and grace.

--Letters of John Newton (ed. Josiah Bull; Banner of Truth, 2007), 71