system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What's actually happening when you miss someone so much you can physically feel it?

Have you ever missed someone so much that it "hurts"? I'd really like to know how the biological aspect of it works. 

Thanks!
gpt
The threshold between mental anguish and physical pain is quite small. That's pretty much what it boils down to. Any emotional turmoil can inflict fairly severe physical effects as well. It's why grief runs rollercoasters over people.