instinctual       
adjective uk/ɪnˈstɪŋk.tju.əl/ us/ɪnˈstɪŋk.tju.əl/
 本能的,直觉的
happening naturally, as a result of instinct, rather than being thought about, planned, or developed by training
  those who struggle to control their instinctual passions 那些难以控制自己直觉情绪的人 
 He says his decisions that day were instinctual. 他说那天是凭本能作出的决定。