I think what consitutes an additional session, is if you FEEL you are having a bad week and can't wait until your next appointment time. I often find that I need a bridge between my sessions and I was going to a group until I couldn't afford it anymore, and now I feel like I need to see more than once a week. But, what I do, before I call asking for an additional session is just try to check in with myself and explore why I feel I need to ask for one. I also try to some ground exercises and meditation to see if that helps, and if it doesn't-I'll ask T if I can come again that week. Most often, T will ask me what I hope to gain from the additional session. Sometimes I just find that hearing her voice on the phone makes all the difference and I just needed to connect.