system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why hurting yourself increases your pain tolerance?
gpt
For pretty much the same reason that taking a drug regularly increases your tolerance, or when a noise becomes regular in your life your brain begins to ignore it (like living near an airport) 

When you are hurt, your nerves send a pain signal to your brain. The more this happens, the less your brain pays attention to the signal, because it filters the pain as "not life threatening".