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Main article: Existential therapy
Sigmund Freud, whom Sartre refuted systematically, was very much affected in so many of his theories by Nietzsche. Some have supposed that Thanatos and Eros were closely related to Dionysian and Apollonian aspects of Nietzsche philosophy.
One of the major offshoots of Existentialism as a philosophy is existential psychology. Sometimes termed the Third Force Psychology, this branch of psychology was initiated by Rollo May and Carl Ransom Rogers, both of whom were influenced by Kierkegaard.
With complete freedom to decide and being responsible for the outcome of said decisions comes anxiety--or angst--about the choices made. Anxiety's importance in existentialism makes it a popular topic in psychotherapy. Therapists often use existential philosophy to explain the patient's anxiety. Psychotherapists using an existential approach believe that the patient can harness his or her anxiety and use it constructively. Instead of suppressing anxiety, patients are advised to use it as grounds for change. By embracing anxiety as inevitable, a person can use it to achieve his or her full potential in life.
Humanistic psychology also had major impetus from existential psychology. Logotherapy asserts that all human beings have a will to find meaning, and that serious behavioral problems develop when they cannot find it. The therapy helps patients handle the responsibility of choices and the pain of unavoidable suffering by helping them decide to give life meaning.