Nobody forces a freewill offering, which is exactly why keeping it decides how much your own word will move you later.
Every promise a person breaks trains their own system to treat future declarations as weather, and once speech carries no weight inside them, the loudest resolution changes nothing by Monday. Tying the volunteered word to Yahweh removes the category of the well-meant intention, the thing one was going to do, and leaves only the thing one has now obligated oneself to do.
A word becomes a must the moment it is spoken, which is why the standard a person keeps in small things sets what they can attempt in large ones. Breaking small words compounds the other way: a person who does it long enough reaches the decision that could change their life and cannot make themselves believe their own announcement of it.