I had a sub who became so "engaged" in our activities and my commands that she essentially forgot everything except wanting more, and more. The first time this occurred, I did not recognize the danger and went further than appropriate (leaving a small but permanent mark that I had not intended). Afterwards I realized that the sub entered her zone and lost contact with the realities of our activities. This realization made me take my responsibility for her safety very seriously. Previously, I had assumed that she would "safeword" when activities became too challenging.

In hindsight, I recommend that you realize that the sub may not use her safeword. This places the FULL responsibility for her limits on you... and you must never lose sight of this when scening with her.