I can relate well to this. I always have it in mind at the beginning of session not to cry. But usually right in the middle of a sentence where I'm saying something about what's recently happening, I'll start feeling tears burn in my eyes and it's out of my hands from that point. I don't talk to anyone else so deeply about my emotions, so I think during my sessions just putting together my thoughts to voice how I feel is enough of a difficulty. The shame and embarrassment for crying doesn't do much to keep me from doing it though.