The brain responds to a stimuli in order to release a series of chemicals that reward the person feeling it with a kick of dopamine equivalent on average to a single standard hit of cocaine.
It then proceeds to motivate you into courting the object of stimuli in question by releasing chemicals that produce negative feelings when not courting them and rewarding you when you are.
Eventually you either succeed in courtship and a relationship is formed of a romantic nature or you fail and the brain further punishes you for that failure.
Alternatively you feel denial, which in the instance of occurance, attempts to ensure continued attempts at courtship.
That would be a perfect system for nature to abide by if it weren't for the fact that rape is illegal... and that having sex with minors is also illegal.
