Maybe that's simplifying it a little. In cognitive-behavioral therapy, the therapist challenges the client's irrational beliefs and gives them exercises and homework to alter their negative thinking. For example, a depressed person might say "I'm a miserable failure", and the therapist would then help the person realize that's an irrational overgeneralization by making the person cite times when they succeeded on a task.
In controlled experimental trials, this kind of therapy works as well or better than drug therapies for anxiety and depression, and tends to have longer lasting effects after the therapy ends.
Miles