A thief may claim that he intended to merely borrow some items.
An embezzler may say he only took a loan.
A person who insulted somebody may say he just used rough language, or was simply joking.
And so, even if I accept the charge of having told a bad joke at a bad time, I will still tend to see the error as much less severe than it actually was.
Therefore, even when one wants to right internal wrongs (if such a thought ever occurs to a person), one nevertheless tends to be lenient with one's self.
In addition, one's reaction to other people's misdeeds is often characterized by strong emotions: shock, astonishment, disgust, and even profound shame.
But when the doer is I, the response is quite different.
Firstly, my personal involvement limits and distorts my ability to see properly.
Personal deeds, like good paintings, must be inspected from a distance.
Secondly, while other people's deeds may arouse disgust, our own hardly ever do.
This applies not only to physical actions or overt aspects of one's personality, but also to hidden thoughts and feelings.
A person's private devils may torment him, but they are never as revolting or frightening to him as other people's are.
–Rabbi Adin Steinsaltz
From "Self-investigations," an essay by Rabbi Adin Steinsaltz