system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why we stop having the urge to cry when hurt during adulthood?

As I remember, when I was small, about 5 years old, whenever I got hurt, I always cried, it was like this uncontrollable urge to cry. Now when I am grown up, I have never cried due to physical pain.
gpt
A newborn cries A LOT. All the uncomfortable experiences/pain they will feel will be the worst pain they have ever felt. They don't have anything to relate it to. As the child grows up, things that previously made them cry don't make them cry because they've experienced it before and are increasing their threshold of pain. 

For example, a 4 year old with a cut on their hand will cry because they might not have ever experienced it before, and the pain might be the most pain they've ever felt on their hand. A 15 year old with the same cut can feel the exact same pain but won't cry because by that point, they've probably felt worse pains. Pain can tend to be pretty subjective.

This is just one factor. Crying is a symbol of weakness, and adults don't like showing weakness (especially males). This is a cultural factor.

Also, adults have a much higher ability to rationalize.