Mishnah 2 in chapter 11 of Nedarim follows directly from Rabbi Yosi's position. In the previous mishnah Rabbi Yosi ruled that the vows listed there are not considered vows of self-affliction, and so the mishnah now asks according to his approach: "V'eilu hen nidrei inui nafesh" - which vows, then, does he include in this category? The answer: things that are difficult for her to bear.
A vow the husband may annul:
If the woman said "Konam peiros ha'olam alai" - all the fruit in the world is forbidden to me - "harei zeh yafer" - he may annul it. Such a vow is considered a vow of self-affliction, and therefore the husband can annul it, and the annulment cancels the vow both with regard to him and with regard to others.
Vows that are not self-affliction:
"Peiros medinah zo alai" - if she forbade upon herself only the fruit of the region where she is living, Rabbi Yosi says: "yavi lah mimedinah acheres" - he can bring her fruit from another region. The husband cannot annul, since there is no self-affliction here: it is in his power to obtain fruit for her from elsewhere. The commentators explain that this applies only where bringing fruit from another region does not involve excessive trouble.
"Peiros chenvani zeh alai" - if she forbade upon herself the produce of a particular shopkeeper, "eino yachol l'hafer" - he cannot annul, for it is in his power to bring her produce from a different shopkeeper.
The exception: "Im lo haysah parnasaso ela mimenu - harei zeh yafer" - if he earns his living only through him, he may annul. When the husband's business dealings are conducted with that shopkeeper alone, and it is he who supplies his needs and even extends him credit and the like, the vow is once again defined as self-affliction, because in the end the matter will weigh upon her and cause her difficulty. Therefore the husband annuls the vow.
In summary: this mishnah sets out Rabbi Yosi's approach to defining vows of self-affliction: a sweeping statement forbidding all the fruit in the world is defined as self-affliction and the husband annuls it; but a limited vow, concerning the fruit of a particular region or the produce of a particular shopkeeper, is not self-affliction, since what she needs can be obtained elsewhere - unless the husband's livelihood depends on that shopkeeper alone. It is worth noting that this is Rabbi Yosi's view, while the Sages disagree and hold that even when she forbade upon herself benefit from one individual alone, it is considered self-affliction, because difficulty is caused to her.