A few minutes ago a couple on SLS asked if I would consider joining them. Cool

, right? Well, the couple asked me to do the one thing I just cannot wrap my libido around. They wanted me to be their (both of them) master. I can't do it. I know. I did it before and over six months I, at 23, started to develop an erection problem. At the end, I actually broke down and cried because I couldn't bring myself to order one of my two women to feed me at a SCA-type event. Even though the sixty+ people who were there suddenly dropped their roles and tried to comfort me, I knew that was one sexual activity I would never be able to do. Even after several dozen free counselling sessions (yes, one of the mistresses was also a clinical psychiatrist), I knew I could never handle THAT much responsibility for someone else's sexual pleasure. The amount of trust given to me was way too much for me to handle.
So, does anyone have an activity that totally turns them off when someone suggests it? I don't just mean something they don't like but something that brings up bad memories and kills their desire to even think about sex until they can calm down?