system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When you're sad why does your chest and stomach hurt/cramp?

Just happens when I get emotional now. It used to be a precursor to tears but I have a really hard time crying so now I just get these achy stabs instead. What are they?
gpt
There's a nerve that runs from your brain to your gut, called the vagus nerve.

The vagus nerve has many functions, one of which is to control parasympathetic functions (mood, digestion, heart rate).

If you are stressed, your vagus nerve can't send signals normally to your stomach. This may lead to digestive irritability and irregularity, which manifests as that feeling in your chest or stomach hurting.