Rabbi Nachman teaches,
When a person repeats a lie twice, it becomes the truth for him. Having repeated it twice, he believes it is the truth. Not only does he deceive himself; he even has the power to deceive others and to cause such intense concealment that it seems as if even G-d agrees with him.
Chayey Moharan #550;
Likutey Halachot, Choshen Mishpat, Genevah 5:11
With permission taken over from: Daily Dose Of Rabbi Nachman