Nedarim 83: If It's a Mitzvah, It's No Gift

What did R. Yochanan mean about partial revoking of vows? With the parallel to nezirut, and how it can't be separated in its vow. Plus, when a woman swears off benefit from others, and the husband cannot revoke that vow, she can indeed eat from leket, shikhcha, and pe'ah - because they're mitzvot. Is the husband included in the "everyone" though? (It's a machloket)