S&M

Intellectual pursuits will always lead one on fresh adventures. The mind can be kept fresh and forever engaged as it confronts and resolves increasingly complex problems.

Repetition of physical pleasures, on the other hand, eventually makes former delights seem dull. So one's appetites turn increasingly towards the exotic, the extreme.

Hence S&M - the requirement for violence with sex, the cruel humiliation of one's partner.

Brutality is an aphrodisiac.
The exercise of raw power thrills.