The master must already have power in the world, the submissive must have power over herself. As a magical discipline, magicians avoid playing with persons for whom this isn't so. To play with such psychic vampires is a drain of power and will murder the soul. Partners who are aware and willing participants produce much more energy, and will effect the world and themselves much more strongly. It takes a mature and focused magician to know the difference between her wants and Needs.
Wants come and go.
The wants we had when were 16 are different than the wants when we were 24 or 32. Wants exist at an animal level. For example, we may think we want the gold of a great job we happen to hear about. So we do our bit with candle and bell and we get it. Unfortunately the job takes up all of our time and is so full of pressure that we can't leave its problems at the office.