Things I know:

Don't try to catch a falling bread knife.

A hot shower on a freezing cold morning may sound like a good idea. It is not. You will be lovely and warm until you shut off the water, then you will wish you were dead. Stay in bed for an extra 15 minutes to try to work up the strength to put some pants on.

If someone you have to see on a regular basis does not share the same views as you do, it is usually best to keep your mouth shut. Smile in a pleasant but dim manner until they stop talking. (Unless they are really just mean assholes, then let them have it.)

It's okay to ignore people on the bus, but be nice to the driver.

Being in a wedding costs a LOT of money. I did not know this until recently.