I'd say don't type out anything you wouldn't want to send, not even as a joke. On multiple occasions I've seen people type a text or email as a joke, and then accidentally send it instead of erase it.

By that same token, don't send things you wouldn't want others to see (or perhaps, be aware of unintended audiences). How often do we hear about nudes being shared? In another example, I once worked at a company that had too many bosses, and one of them shit talked me to my boss in an email. They replied back and forth a bit, and then my boss had a question for me about the project they were now discussing, so he forwarded me the entire email chain. I saw exactly what the other boss said about me, and there was no denying he was the one who said it. I immediately and permanently lost all respect for him.