some things are better left unsaid

Some things are better left unsaid is another way to say that some things should not be discussed, often referring to a thought that everyone is also thinking, but bringing it up would cause some sort of difficult if it was talked about in public. This could be something everyone is thinking but it would be in appropriate to speak about in front of others or to say out loud, or perhaps a response to someone who has brought something up which shouldnt have been said in the first place.