Evolutionist jellies: Humans are the only species that cries as a result of strong emotion. I'm curious how you explain this.

First of all, I don’t want this to be a creationism/evolutionism debate. I simply want to see what an evolutionist’s explanation of how we evolved this species trait.
My thinking is:
Crying relieves stress and it gets manganese (a chemical depressant), leucine-enkaphalin (chemical which helps control pain), and the adrenocorticotrophic hormone (a chemical produced by bodies under stress) out of the system. This makes you feel better. By releasing these chemicals, you actually feel less depressed. What possible survival benefit does this have? I would think that bottling these emotions up makes you more aggressive, which would make you more fit for survival. Wouldn’t this particular feature get removed out by natural selection, then?

Again, I simply want to hear an evolutionist’s thinking on this subject.