Self-deception is so common. We experience it all the time in those who are close to us inasmuch we consider ourselves immune to that.
In Christian belief there is a good practice called an examination of conscience. You sit down alone in quite place and think about what you have done. And listen what the inner voice tells you about right and wrong.
More convenient title for this would be an examination of one's past. We can't change the past but insted it changes us. Burns us from within or makes us better. The former scenario comes from denial the latter through confession.