Essentially, it is the act of telling one's self (or a group telling themselves) something that they consider to be true, or to convince themselves, with the unfortunate repercussion of their having no doubts. Because of what they do to themselves, they will go over every aspect of their side of the "argument" to prove to themselves that they are right, and will refuse to look at any alternatives. Self-propaganda is a form of self-deception. It functions at individual and social levels: political, economic, and religious. It hides behind partial truths and ignores questions of critical thought.
The psychological process of utilizing self-propaganda can negatively influence values and beliefs, and subsequent perceptions and judgments, thus becoming a self-fulfilling prophecy.