Our Gemara on Amud Aleph discusses a famous halakhic and Jewish legal principle:

תּוֹךְ כְּדֵי דִיבּוּר – כְּדִיבּוּר דָּמֵי

The legal status of a pause or retraction within the time required for speaking a short phrase is like that of continuous speech. Meaning to say, essentially one can retract something that was said, if done so immediately.  This has many applications in both Jewish civil law and ritual law, that certain statements uttered do not count if immediately retracted within the time span of כְּדֵי שְׁאֵילַת שָׁלוֹם תַּלְמִיד לָרַב the time necessary for a student to inquire after the welfare of his rabbi. This is known as Toch Kedei Dibbur. 

Though some poskim disagree, the Shach holds by the general Talmudic principle that within the time it takes to utter “Shalom Alecha Rebbi[U-Mori]”, “Peace onto you, my master [and teacher]”, almost all forms of speech and utterance is reversible. (See for example Shulkhan Arukh YD 210:3. Also note there is a disagreement about if the length includes the last word, “U-Mori” “My teacher” see Mishna Berura 124:34).  

There is some debate as to why speech is reversible within that time frame.  The least lomdishe peshat is that since that is a normal part of the cadence of speech for thoughts to formulate and be expressed, it is also considered as one simultaneous utterance, even though not technically at the same time.  Others say the rabbis either enacted, or intuited, a standing assumption that a person does not fully affirm what he is saying until he has a moment to re-think it. Thus the given assumed condition is that whatever he says is conditional, until that momentary pause.  Some cleverly explain the reason for using the greeting to the rabbi as the measurement for this length of time is based on an assumption that a person’s rabbi might pass by while he is talking or engaging in commerce, and he would feel compelled to interrupt and greet his rabbi.  Thus, no verbal declaration should be valid until that moment passed, as he might have wanted to reverse his statement, but first had to acknowledge his rabbi. (See (תוס' בבא קמא עג: ד"ה כי,  נדרים פז. ד"ה והלכתא Ran Nedarim 87a, and Rashbam Bava Basra 129b and Ritva Nedarim 86b).  

The Shach notes, there are four exceptions where an utterance is taken as permanent and affirmed and cannot be reversed, even within Toch Kedei Dibbur, based on Gemara Nedarim (87a):

וְהִילְכְתָא תּוֹךְ כְּדֵי דִבּוּר כְּדִבּוּר דָּמֵי חוּץ מִמְּגַדֵּף וְעוֹבֵד עֲבוֹדָה זָרָה וּמְקַדֵּשׁ וּמְגָרֵשׁ

The Gemara concludes: And the halakha is: The legal status of a pause or retraction within the time required for speaking a short phrase is like that of continuous speech, and so a person can retract what he first said if he issues the retraction within this period of time after he finished speaking. This principle holds true in almost every area of halakha, except for the case of one who blasphemes God; or in the case of an idol worshipper, who verbally accepts an idol as his god; or one who betrothes a woman; or one who divorces his wife. In these four cases, a person cannot undo his action, even if he immediately retracts what he said within the time required for saying a short phrase.

While there are slight differences in explanations by the commentaries as to why these four are different (see Ran ibid and other commentaries on the Daf), more or less the idea is that since these are such serious an weighty matters, the person either is resolute before he says it, or the rabbis did not want to allow the person any lee-way.  Regardless, one can see al-derech derush and derech seichel, that the two themes are marriage and idolatry.  Both of these have to do with relationships that are covenantal and committed, the Jewish nation’s marriage to God, and the flesh and blood union of Man and Woman. In either, apparently, betrayal is so serious that even a momentary lapse is unforgivable. 

There is a basic biological process that is hardwired in our brains to attach more weight, validity and significance to negative statements than to positive statements.  This is because the organism stands more to lose by ignoring a potential threat than by ignoring a potential benefit.  Think about it, if one suspects they are about to be attacked by a murderer, even if it is just a suspicion, there is potentially a high penalty to be paid by ignoring the threat.  If, on the other hand, you suspect that someone is about to give you a million dollars, if you ignore it, there is no damage other than a lost opportunity. Therefore, our minds are automatically hardwired to give more credence to negativity and this is why bad news travels so much faster than good news.  This is also why we tend to believe insults more than we believe compliments.  The bottom line is that this is the mental equivalent of an optical illusion.  It feels true, but it simply is not so.   When people are angry, indeed they are less inhibited and can say hurtful things.  There must be a degree of truth to what is being said, otherwise it would not be said. However, when people are angry they also want to hurt the other person, which means that not all of it has to be true.  In addition, positive and loving statements said at other times may be no less true.  

While the halachos of what is retractable are not up to us, in personal matters of relationships, we can forgive and agree on any reasonable and fair conditions. (This idea is reflected in Halacha, see Bava Metzi’a 94a and Shulkhan Arukh EH 38:5). You and your spouse can make up and agree that once in a while, a person can get a “get out of jail free card”, where one can ask for amnesty and reversal of what was said or done.  If you have this agreed on in advance, it can help everyone let go, forgive, and emphasize positivity and repair instead of continuing a downward spiral.