St. Teresa of Ávila (top left) had much to say on holy speech, but it was summarized by an anonymous Jesuit (a loyal son of St. Ignatius of Loyola, top right) in a book now called Practical Meditations.  I know this is a short article for the second half of this week, but I found every sentence extremely convicting, so, I hope you do, too.  He summarizes her as writing:

Speak little, especially when you are with many people.  Never praise yourself, your knowledge, your good actions, or your birth, unless you have reason to hope that it may be of use, and then do it humbly, remembering that these are all the gifts of God.  Never excuse yourself, unless there is some strong reason for doing so.  Avoid all disputes, and especially in things of little consequence.  Speak to everybody with quiet cheerfulness.  Never exaggerate things, nor assert anything without being very sure of it.  Never speak without thinking what you are going to say, that nothing which can offend may escape you.  When anyone speaks on spiritual subjects, listen to him with humility.  In your discourse, and in the conversations in which you have to take part, always mingle some words which treat of the spiritual life, for by this you will avoid idle words and detraction.

As always, please pray that I may practice what I preach.