How do you decide what's safe to paste into ChatGPT/Claude?

I keep noticing people, myself included sometimes, paste things into AI chat tools without a second thought. A contract, a customer email, a snippet of code with an API key still sitting in it.

Do you have an actual personal rule for what you will and won't paste into an AI tool? Or is it more of a "gut feeling in the moment" thing?

I ask because I work in information security and AI safety, and this is one of those questions that comes up constantly with non-technical friends and coworkers. There isn't really a simple, agreed-upon answer yet.