So Far, You Didn’t Sin Nazir 62 Psychology of the Daf Yomi
Our Gemara on amud aleph makes a statement about annulment of vows that is said many times throughout Shas: הֶיתֵּר נְדָרִים פּוֹרְחִין בָּאֲוִיר “The halakhos of dissolution of vows, namely that one may request from a halakhic authority to annul them, fly in the air and have nothing to lean upon, i.e., these halakhos are not mentioned explicitly in the Torah.
Sefer Arvei Nachal (Noach 2, 5663) understands this phrase as hinting at a deeper truth regarding oaths, words and intentions. When a person makes a commitment that he has yet to fulfill, it is neither true nor false, it literally is hanging in the air. This is the key to the ability to annul the vow. Since he has not yet performed or not performed said commitment, if he has a sanctioned ability to retract it, he has committed no sin as of yet.
So while it is unwise and improper to make oaths, the rabbinic ethic is to try to annul the oath if you are not sure you can keep it, because you haven’t really sinned yet.