I will be responsive to my Master. I will not hide what my mind and body are feeling so that i my assist my Master in his responsibilities as my authority. I realize that my Master is not a telepath, and will not expect my Master to know thoughts or feelings which i do not share.
I'm fairly easy to read, emotionally, with my heart always on my sleeve. I may try to hide, but for someone who knows me, these attempts are usually useless. Still, i have a tendency to say 'i'm fine' when asked what is bothering me, or to cover up pain and sickness. I often refuse to disclose my thoughts and fears, my anger or frustration, until it is either too late or everything comes out in an explosion of discontent. Not only is it hazardous to my mental and physical health to both hide and explode in rage, but it is also hazardous to relationships. I don't think that anyone really enjoys being blindsided by an emotional 2x4.
Hiding what my body is feeling can, in extreme cases, cause serious physical injury. A Dominant may scene harder than is healthy for a submissive if he doesn't know that she is suffering from a health issue. Here is an example. If you are a dominant that has not been told the medical history of the submissive you are playing with, you could be aware that she has blood sugar issues. During an intense scene, her blood sugar drops, heart rate and breathing slow and she falls unconscious. Time is wasted in panic and then 9-1-1 is called. This could have been avoided with glucose tablets, which raise blood sugar quickly. In this situation, the blame lies with both parties. The girl obviously should have communicated with the dominant she was playing with. However, i believe it just as important for the dominant to ask any potential playmates about medical issues, as for a submissive to volunteer the information. Master of Reason, for example, took note of my medical history before we ever played seriously. It keeps both of us safe.