Reading in one of the blogs I keep an eye on (I didn't say I read it thorougly all the time, I just keep an eye on it) I stumbled upon the acronym THINK. It refers to five qualities that what you write should always have, especially when you're communicating with other people.

Each time you are writing, or at least before you rush to the "Send" button in your MTA, you should consider if what you have just written is:

Thoughtful
Honest
Intelligent
Necessary
Kind

I admit I sometimes sin with T and N, and in the worst case with K 😦