Unfortunately we have to overcome both instinct, motivation, and willpower.
Motivation is never something to overcome. Motivation is power. You work with it.
By "willpower" people usually mean ability to force yourself to do something you aren't motivated to do - you shouldn't try to do that, it's operator error of the human system.
Fear of spiders and snakes were found in infants.
Reflexes are instinctual.
I think we have a few instincts.
The problem with claiming that humans have instincts is that it gives cover for bad theories of mind. For instance, the Nazis believed Jewish people have Jewish minds and German people have German minds; many Marxists have held that bourgeoisie have bourgeois minds. In reality, the human mind is a blank slate, in terms of knowledge and beliefs.