Scientology creates a personal and shared delusion that the compulsive and obsessive introspection of oneself (with the pseudoscience of past life memory regression sprinkled in) can lead to a "cleansing" or "suppression" of the unconscious and subconscious mind.
"Whatever is true for you, is true for you." = Solipsism: the view or theory that the self is all that can be known to exist.
The most frightening (and borderline illegal, definitely immoral) aspect of this "faith" is that their methods of introspection and counseling (auditing) are directly stolen from the field they purport to despise. Auditing is a bastardized form of psychoanalysis where the trained and licensed therapist has been replaced by an agent of the church who has ulterior motives to drive you further into the "faith" or "process."
You will see gains and "wins" but that is the power of psychoanalysis, not scientology. They will use these gains, which they condition you to believe are the direct result of your involvement in the church, to create a strong, personal, and emotionally manipulative confirmation bias.
Its the ultimate bait and switch: Demonize the field of psychology, steal their therapeutic methods--which have the weight of the scientific community, i.e. more than one author and PEER REVIEW--then attribute the real benefit that these methods give to patients to the "church."
Their hatred of psychology also creates an "air tight" defense (delusion) against critics. Critics who are well informed about the evolution of psychology and common cognitive errors/biases will be driven mad trying to explain the reality of Scientology in terms of biases, errors, and manipulation. They will gleefully try to destroy your sanity... even though they are expressly forbidden by their religion to destroy the sanity of another.