Why the Truthful One Views Himself as Someone Deficient – By Ibnul Qayyim [rahimahullaah]
The truthful slave does not see himself except as one who is deficient, and what necessitates this view are [the following]: He [considers what] he seeks after [i.e. sincerity, obedience to Allaah and His Messenger etc] to be great; [considers] himself insignificant and knows his defects, and [considers] himself as having sent forth little deeds for the Aakhirah.
[Madaarij As-Saalikeen 2/293. abridged]