I wouldn’t dare defile Douglas Adam’s memory by not mentioning that you should keep a towel with you at all times, but my second contender is a surprisingly short three-parter:
- never lie.
- never tell the whole truth.
- never pass up a chance to use a real bathroom.
This is dumb, and in many cases outright illegal.
If you are giving testamony in court you are required to tell the whole truth regarding the situation.
There are absolutely other times when you should tell the whole truth, so this statement is just dumb.
Even in court you have to use some judgment to determine what the whole truth is, under what context, and to the extend of your memory or a reasonable expectation of enforcement of the idea.
There’s also limitation with self incrimination/5th.
But as a generality, omitting information on socials, whatever registration form, etc… In everyday life is a reasonable practice for preserving privacy.
Being dishonest with friends & family is messed up tho.