Want to reveal a Secret = keep mouth tight.

People always have an urge to tell something. Especially about a secret about a good friend.

They tend to reveal to a person with a strong indication not to replay the same. When the teller leaves the place, the listener's first duty to is to reveal it. That also to the person about whom the matter is told.

So if you are in the habit of revealing something, put an end to that habit. Because it is the ideal of others to earn a good name and to it they want to discredit the one who told something, especially offensive about others.

On the other hand talk about someone highly in his absence, you can be very sure, it will never reach the other person.