The animal soul, is the source of all your self-serving drives. In one word, the animal soul is self-centered passion.   But our yetzer hara takes the raw material of the animal soul's benign passion and provides it form by channeling it towards immoral ends.  The animal soul naturally gravitates towards that which it perceives as pleasurable and gratifying. As physical beings, our default pleasures are physical, and often of the forbidden variety.  Rabbi teaches us how to control it.