Keep your mouth closed until your mind is in gear.

I went down with the ship but I kept my mouth shut so I didn't drown like the rest of them.

You are a slave to what you do say, a master of what you don't say.

Consider the whale: It never gets into trouble until it comes up and starts spouting.

I don't know whether to keep silent and let people think I am ignorant or open my mouth and release all doubts.

There's nothing wrong with having nothing to say -- unless you insist on saying it.