Keeping quiet is usually a good idea
If you refrain from making a vow, you'll avoid sin וְכִי תֶחְדַּל לִנְדֹּר לֹא יִהְיֶה בְךָ חֵטְא
This is very much like the type of advice one finds in Koheleth (or Qoheleth if you prefer). As in 5:5-6 טוֹב אֲשֶׁר לֹא תִדֹּר מִשֶּׁתִּדּוֹר וְלֹא תְשַׁלֵּם
אַל תִּתֵּן אֶת פִּיךָ לַחֲטִיא אֶת בְּשָׂרֶךָ וְאַל תֹּאמַר לִפְנֵי הַמַּלְאָךְ כִּי שְׁגָגָה הִי
Shlomo seemed to know that the wise man is careful about his words and doesn't promise what he can't deliver. (It goes without saying that anyone who runs for office must be lacking in such wisdom.) The Torah itself doesn't typically include that kind of advice in its accounts of mitzvos. One usually has to infer that something may be a bad idea, as in the juxtaposition of the eshes yifat toar to the ben sorrer umoreh in our same parsha.
Related post: http://kallahmagazine.blogspot.com/2016/09/earthly-and-heavenly-justice.html