My horse had a hissy fit when we took the other horse out today?

so i took my horse out and gave him a bath then i felt like i was leaving my friends horse out because i don't like her so i decided to take her out and brush her and as soon as i put my horse back in the pasture and gave him hay , i took windy(the other horse) out he started running around , bucking and whinnying really loud , how do i get him to stop misbehaving like this when i take windy out of the pasture ( there the only 2 in the pasture) plz help