Rav Elyashiv is quoted as saying that the text of the viduy, “May it be Your will that I will not sin again” recited at the end of the viduy on Yom Kippur qualifies as a resolution for the future. How can a tefillah serve as a vow or resolution?
Rabbi Luxenberg shlita explains (Droshas Shabbos Shuva, Neos Simcha 5778) that one can only do what is in his power to do. The yetzer horah, we are told in Kiddushin (30b) “overpowers him every day, and seeks to kill him, as it is stated: “The wicked watches the righteous and seeks to slay him” (Tehillim 37:32). And if not for the fact that the Holy One, Blessed be He, assists each person in battling his evil inclination, he could not overcome it, as it is stated: “Hashem will not leave him in his hand (Tehillim 37:33).” So really, the only way to overcome the yetzer horah is to daven for Heavenly assistance. And davening for it is the only action that can help to stave it off, which is in essence an expression of that future vow.
This is also the Rambam’s approach (Hilchos Teshuva 6:4) – the way to achieve teshuva when there are obstacles on the way is to daven to Hashem.
