The realization that existence is a process, a 'becoming', helps to avoid the temptation to see man as a collection of 'mechanisms' which, when faulty, can be overhauled or dismantled. Therapy takes place in a present which contains the past and is directed towards a future. Undue preoccupation with the past and the neglect of present phenomena and future possibilities tend to restrict the understanding of the problem as it 'presents' itself. Man is able to choose, within the limits of his/her conditions, and has responsibility for this choice. The possibility of change is closely bound up with that of choice, and change is at the very heart of therapy. But to choose makes us feel anxious, and not to choose makes us feel guilty. An existential approach needs to introduce the concepts of existential anxiety and guilt, as distinct from their neurotic counterparts. If it is accepted that all experience is interrelated, the examination of isolated events will prove limited and even misleading. Particularly, the existential assumption of interrelatedness will sharpen the psychotherapist's awareness of the fact that s/he can never be an 'objective' observer, that (whatever his/her method) there is a living relationship between therapist and patient in which influence and change are mutual.(ABSTRACT TRUNCATED AT 250 WORDS)