"monkey of the heart/mind and horse of the ideas/will" Monkey mind is kind of a put down for monkeys, but accurate to describe humans in the flight(y) mode.

Ironic the horse is the metaphor for the will; a prey animal given to flight first, herd mentality, can be addicted to learning by a skillful trainer, and is probably the most liked animal behind dogs for its physicality and disposition. Having eight months of near daily experience of "bail of hay in, bucket of poop out" for 25 horses, I did learn a bit of their wonder and complexity.