A "speech fast" (ta'anit dibbur) is one of the more radical tools in the arsenal of self-improvement developed by Jewish pietists over the centuries. Words, the medium that most express our divine uniqueness, are so easily devalued. Empty chatter is everywhere, but real conversation is rare. Pirkei Avot enumerates miyut sich, limiting talk, as one of the 48 ways through which wisdom is acquired. The speech fast aims to restore awareness of the preciousness of words through a period of voluntary abstention.
Some mystics still have the custom of assuming a ta'anit dibbur, refraining from idle conversation during the 40 days from the beginning of Ellul until Yom Kippur. This is not something you should try at home without the authority of a competent rabbi - people might think you are weird. But an hour or two of silence can help return us to an appreciation of the divine power of speech.