Both my psychiatrist and therapist give a signal to begin wrapping up the session. They both do a quick summary of what we discussed and things to work on. In the case of my therapist we actually speculate about what to put on the following week's agenda (she makes copies of her notes for me too). She walks me to her assistant's office and communicates when she'd like to see me next and then walks me to the door of the clinic. In neither case is the closure of the session done abruptly.