Depression and anxiety are common disorders in older adults. For some, even after a combination of pharmacological and psychological treatments, residual symptoms and periodic relapse persist throughout the lifespan. This pattern can lead to pessimism, as well as an increasing deficit in euthymia. Well-Being Therapy is an innovative approach to addressing depression and anxiety symptoms that are often influenced and accompanied by low levels of psychological well-being. The core principles of well-being therapy, as well as the related concepts of euthymia, eudaimonia, and psychological well-being, are described and illustrated.