system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it so painful to accidentally bite your own tongue but when you purposefully bite it, it doesn’t feel like anything?
gpt
The reason is because when you bite down on your tongue on purpose, you aren’t actually biting down as hard as when you bite on your tongue accidentally.

Your brain knows you are about to hurt yourself, so even if you don’t realize it, when you bite down on your tongue on purpose, you aren’t biting down as hard.

It’s that simple.