Fiery reformer John Knox was keenly aware of his own shortcomings:

Although I never lack the presence and plain image of my own wretched infirmity, yet seeing sin so manifestly abounds in all estates, I am compelled to thunder out the threatenings of God against the obstinate rebels. In doing whereof (albeit, as God knoweth, I am no malicious nor obstinate sinner), I sometimes am wounded knowing myself to be criminal and guilty in many, yea, in all things that I reprehend in others. Judge not, mother, that I write these things, debasing myself otherwise than I am--no, I am worse than my pen can express.

In body you think I am no adulterer. Let so be, but the heart is infected with foul lusts, and it will lust although I lament ever so much.

Externally I commit no idolatry, but my wicked heart loveth itself and cannot be refrained from vain imaginations, yea, not from such as were the fountain of all idolatry.

I am no man-killer with my hands, but I help not my needy brother so liberally as I may and ought.

I steal not horse, money, or clothes from my neighbor, but that small portion of worldly substance I bestow not as rightly as his holy law requires.

I bear no false witness against my neighbor in judgment or otherwise before men, but I speak not the truth of God so boldly as it becomes his true messenger to do.

And thus in conclusion, there is no vice repugning to God's holy will expressed in his law, wherewith my heart is not infected.