” We should learn from our mistakes, but we shouldn’t beat the tar out of ourselves over them. The past is just that, past. Learn what went wrong and why. Make amends if you need to. Then drop it and move on.
—Sean Covey
The Power of Speech
Judaism is intensely aware of the power of speech and of the harm that can be done through speech. The rabbis note that the universe itself was created through speech. Of the 43 sins enumerated in the Al Cheit confession recited on Yom Kippur, 11 are sins committed through speech. The Talmud tells that the tongue is an instrument so dangerous that it must be kept hidden from view, behind two protective walls (the mouth and teeth) to prevent its misuse.
The harm done by speech is even worse than the harm done by stealing or by cheating someone financially: money lost can be repaid, but the harm done by speech can never be repaired. For this reason, some sources indicate that there is no forgiveness for lashon ha-ra (disparaging speech). This is probably hyperbole, but it illustrates the seriousness of improper speech. A Chasidic tale vividly illustrates the danger of improper speech: A man went about the community telling malicious lies about the rabbi. Later, he realized the wrong he had done, and began to feel remorse. He went to the rabbi and begged his forgiveness, saying he would do anything he could to make amends. The rabbi told the man, “Take a feather pillow, cut it open, and scatter the feathers to the winds.” The man thought this was a strange request, but it was a simple enough task, and he did it gladly. When he returned to tell the rabbi that he had done it, the rabbi said, “Now, go and gather the feathers. Because you can no more make amends for the damage your words have done than you can recollect the feathers.”
Speech has been compared to an arrow: once the words are released, like an arrow, they cannot be recalled, the harm they do cannot be stopped, and the harm they do cannot always be predicted, for words like arrows often go astray.
http://www.jewfaq.org/speech.htm