Our Gemara on amud aleph discusses what legal assumptions can be made when a borrower claims to have paid back a loan, but the lender refuses. 

גְּמָ׳ אָמַר רֵישׁ לָקִישׁ: הַקּוֹבֵעַ זְמַן לַחֲבֵירוֹ, וְאָמַר לוֹ: ״פְּרַעְתִּיךָ בְּתוֹךְ זְמַנִּי״ – אֵינוֹ נֶאֱמָן; וּלְוַאי שֶׁיִּפְרַע בִּזְמַנּוֹ. אַבָּיֵי וְרָבָא דְּאָמְרִי תַּרְוַיְיהוּ: עֲבִיד אִינִישׁ דְּפָרַע בְּגוֹ זִימְנֵיהּ – זִימְנִין דְּמִתְרְמוּ לֵיהּ זוּזֵי, אָמַר: אֵיזִיל אֶיפְרְעֵיהּ כִּי הֵיכִי דְּלָא לִיטְרְדַן,

Reish Lakish says: If a lender set a time for another to repay the loan that he had extended to him and when the debt came due the borrower said to the lender: I already repaid you within the time, he is not deemed credible, as people do not ordinarily repay their debts before they are due. The Gemara rhetorically comments: If only the borrower should repay his debt on time!  Abaye and Rava disagree with Reish Lakish, as they both say: A person is apt to repay his debt within its time, i.e., before it is due. This is because sometimes he happens to have money and the borrower says to himself: I will go and repay my debt so that he will not trouble me later by constantly demanding the money.  

It is notable that Reish Lakish, or the editors of the gemara added the rhetorical comment, “If only the borrower should repay his debt on time!”  The tendency for people to aggrandize their intentions when their actual actions fall short is unfortunately endemic to human nature, and even more in regard to money, when temptation is always high. Our sages have noted that the righteous say little and do much, while the wicked say a lot but do not follow through on even a little (Bava Metzia 87a). 

Psychologically speaking, when a person is overly affirmative about their intentions, it may be a reaction formation and betray ambivalence or conflict over it.  We find Gemaras where an overenthusiastic agreement is taken to actually signal misgivings and dissent, having halachic implications for determining binding and full intent in financial transactions (Bava Metzia 22a, “klach etzel yafos”). In addition, by engaging in a verbal fantasy about what the person promises to do, it discharges some of the psychic energy and motivation to do the work. The imagined achievement becomes a substitute for actual achievement.  When I was a child, my father Z”L used to say to me, “Don’t commit to a mitzvah too loudly, as the Satan will overhear and try to stop you.”  My father was being cute and psychologically deep at the same time. He meant to say, the more you talk about it, the less you will tend to do it.   He would explain: “Don’t allow yourself the satisfaction of talking about it too much until after you achieve it, or you’ll get distracted in the day dreams of having accomplished it, when in actuality, as of yet, you did not.”