It's often said that ancient Hellas was the birthplace of modern medicine, but it's important to note that ancient Hellas was also the birthplace of psychology and the relations between biology and psychology. Take for, example, Hippocrates in On the Sacred Disease:

"People should know that our pleasures, happiness, laughter, and jokes from nowhere else [but the brain] and that our griefs, pains, sorrows, depressions and mourning come from the same place. And through it we think especially, and ponder, and see and hear and come to perceive both shameful things and noble things and wicked things and good things as well as sweet and bitter, at times judging them so by custom, at others by understanding what is advantageous based on distinguishing what is pleasurable and not in the right time and [that] these things are not the same to us.

By this very organ we become both sane and delirious and fears and horrors attend us sometimes at night and sometimes at day. This brings us bouts of sleeplessness and makes us mistake-prone at terrible times,  bringing thoughts we cannot follow, and deeds which are unknown, unaccustomed or untried." [14]

All right, he was very off in the part that follows (which has to do with wet brains and biological process we've long debunked), but all of this makes sense. If you find yourself struggling emotionally, remember: the ancient Hellenes already knew that it was just your brain acting up. I don't know about you, but that's a comforting thought.