Some people often suffer from a certain idealization of the "perfect Jew," based either on living models glimpsed from a distance or archetypes out of the past.
Such a person is imagined to be completely at one with himself and his chosen path, knowing no failure in its pursuit.
Comparing himself to this ideal figure, the stumbling ba'al teshuvah (newly observant Jew), for example, experiences radical self-doubt.
The truth is that such ideal types, people who know no backsliding, have never existed except as figments of the imagination and of literary invention.
No Jew, even the greatest leader, saint, or prophet, has ever been free of religious problems, failings, heartaches, and doubts.
This is an established principle: everyone who takes the religious life seriously and who is thus ever striving onward experiences setbacks along the way.
It is not merely that "there is no one so righteous that he does only good and never sins," but more than this: temptation, doubt, pain, and transgression are the inevitable lot of those who would ascend higher.
–Rabbi Adin Steinsaltz
From Teshuvah, p. 36, by Rabbi Adin Steinsaltz