there are a lot of theories about what people get from cutting. here are some of the factors that have been thought to be involved:

- people often have a 'faint' response to blood (especially their own). the thought is that ones heart beats a little slower so that less blood is lost (this is thought to be the function of the fainting response and perhaps the shock response too). this could have a arousal regulating effect.
- endorphins are released because of the pain. that is how come people sometimes don't really feel the pain. that also has an arousal regulating effect.

maybe... part of your concern is that if you let out the emotional pain in his office he won't be able to help contain your emotion so you can return to emotional baseline. maybe... the images of cutting make it feel a little bit safer that you could share the pain with him. because if you cut then you will be able to contain it / regulate yourself back to emotional baseline.

just a thought. i could be off.