How can I be such a mess all week but then seem ok in session?

I sometimes visualize how I want a session to be, and in my mind I'm very animated in expressing my feelings. I just did this yesterday. I enacted an entire scene with me saying emphatically to T "I don't love YOU! You're nothing to me. It's my mother I love! I miss her! "She's the only one who really loved me!" I'm in a rage, crying in emotional and physical pain ( I was in physical pain when I was visualizing this scenario) and T had tears in her eyes, saying "let it out". I've never cried in therapy.

Suffice it to say, when I see T that scene will never occur. The most that will happen is that I TELL her about it with no emotion and no tears. Kind of matter of factly. I can see the dramatic scene in my mind right now, but when I get to the office it disappears.

OMG! I am the same way! I have dropped in to the pits of despair, an emotional wreck, and by the time I see T, I'm fine again. I tell her what my time has been like and I'm totally flat and matter-of-fact like rainbow8 said. There's no emotion. I went once, and I wanted to tell her about my fabulous weekend. Instead, I drew a blank.

I have been journaling and I figured I could make a list of things to tell her. I just never do. Why? It's always the same thing, different day. The last time she asked how things were, that's exactly what I said! Same thing, different day.