Everything we write may eventually become public at some point in the future.
Maybe the original recipient decided to share it with someone else. Or perhaps the online services we use got hacked.
Maybe it happens after we pass away, and someone has to go through our laptop or cell phone to decide if something’s worth keeping. Maybe it’s after one of our correspondents passes away and someone has to sort through their laptop or cell phone and finds our messages there.
We should be thoughtful and intentional in our communications.
PS: Another simple and related rule: if you are talking about a third person, do it so that if the person were present, he or she would not have anything to complain about.