I read somewhere, once, that crying defies scientific explanation. Tears are only meant to lubricate the eyes. There is no real reason for tear glands to overproduce tears at the behest of emotion.
I think we cry to releast the animal parts of us without losing our humanity. Because inside me is a beast that snarls, and growls, and strains toward freedom, and, above all, toward life. And as hard as I try, I cannot kill it.
So I sob into my hands instead.
— Veronica Roth, Insurgent