Ambivalence means the coexistence of two opposite feelings or impulses, usually love and hate, towards the same person. A young child with undeveloped ego-strength is unable to tolerate his own ambivalent feelings towards the same person, for instance towards a mother who is sometimes kind and loving and sometimes rejecting and cruel. He might end up by splitting his feelings and perceiving her as two, the "good mother" and the "bad mother".
In analytic psychotherapy the boundaries help to hold the whole spectrum of emotions together from one extreme to the other. All analytic therapies, short-term or long-term, open-ended individual therapy, or group therapy conducted along analytic lines, are designed to explore emotional ambivalence. The healing emotional experience consists in discovering that each of us, and our relationships, therapeutic or otherwise, become stronger once we stop splitting the positive from the negative, once we stop hating on the one hand and over-idealising on the other.
The time to try to integrate the opposite feelings is when a patient is deeply engrossed in a memory about a much loved or hated person. For instance, the patient remembers his father being terminally ill and the therapist reminds him: "You love that frail body, but when you were a child you also hated him for beating you up..." For the sake of psychic health, opposite feelings have to be kept together in struggle and in harmony.
See also BADNESS, BASIC FAULT, "BREAST", DESTRUCTIVE IDEALIZATION, EGO-STRENGTH, FEELING, GUILT, REPARATION, SPLITTING