Let us guard our mouth constantly, set reason on it to close it, not for it to be constantly closed but for it to open appropriately in season;  there are times when silence is of more value than speech, as likewise speech more than silence.  This is the reason why that most sage composer said, ' A time for keeping silence, and a time for speaking.'  After all, if being open at all times was necessary, there would be no doors, while if being closed was required at all times, there would be no need of a guard.  I mean, what would you guard if things were closed up?  Door and guard are for this reason, however, for us to use each at the proper time.

St. John Chrysostom