I think eventually we do get angry and deal with that anger right away but until then we still have the mothers and the anger we didn't deal with in the moment. That's probably why we discuss the old and deflected stuff in therapy for a long long time before we get to the immediate, "hey, therapist, you %#@&#! me off right now!" stuff. Old is familiar so probably instead of telling your friend she annoyed you, you kicked your therapist :-) by being angry/sullen in therapy because you know now she won't reject you but too, your therapist is more familiar as an object of your mother than your friend is?