We have a complex stack of control mechanisms. Intellect on top of emotions on top of instincts on top of reflexes on top of autonomous processes (which are layered too). The lower you go the less control you have and the more primitive the capabilities are. Reflexes and below don't even involve the brain.

While instincts are mostly concerned with immediate survival of the individual and the continuation of the species, most interpersonal, society-forming behavior is regulated by emotion. A lot of our identity lies there - belonging, love, likes and dislikes, connection, who we're comfortable with, who we open up to, but also hate, revenge and callousness.