Not to gain more power over horses but to have a better relationship with them but mostly to become a more calm centered individual who can respond to stresses/conflicts in life without all of the drama/fighting.
Well...who said 'power over' anything or anyone? Power (especially in the IP/aiki sense) is power within oneself--capacity, ability. Misunderstanding of aikido leads to fear of nature, itself. Power over fear, however...that's another thing.