The worst advice for a startup founder.

"Don't tell anybody about this"... I think this is bad advice. Even if you're working on GPT-5, there's a good chance the people you'll talk to about your new idea will either not care enough to pay attention or just don't understand it at all. But there's a slim chance that somebody who you share your idea with will become your partner/co-founder/investor, etc. This was the case for me and ever since, I am always happy to share my ideas with everybody.