In a whole year, I never had to leave to use the bathroom mid session. Yet, 3 weeks ago, 2 sessions in a row, I had to pee soooooooooooo bad, like I could not focus, and I asked if I could go. My T's practice is pretty wierd though, it is in a building with another business (I think some sort of machine sales) and there is a halway separating the two. So the bathrooms are in the hallway...I have to go out of T's office, through the waiting room, out the main door and into the hallway...pretty inconvient if I'm already in session! I try to go at the beginning if I have time, but it can be an nerveracking situation and I'm only human!