Why can't a man touch a woman's waist in the morning?

Some men believe in Feng Shui, but they don't mind others touching his head, especially women, because being touched sometimes has a bad day, which is also related to psychological effects, but sometimes it is really weird. As for a woman's waist, in fact, there is really nothing to be touched. If a man's head is also a woman's foot, how can it be a waist?