It's inevitable, isn't it? If you're not sweating, then either the room isn't warm enough for your client, or you're not working hard enough! Or maybe you're a naturist and undressed (see naturism thread...).
Last year I went on a No Hands Massage course and its originator, Gerry Pyves, who was leading the course, talked of us thinking about pouring out gold into our clients when we massaged them. It was a very warm room and the massage is very physical and at first I was alarmed about dripping sweat on to the clients' skin. After a while, I realised that they didn't even notice - so started to think of it in terms of pouring out LIQUID gold on to my clients...