Chazal tell us that as a result of the sin of not keeping nedarim a person's children can die. Ayom v'nora, a tragic punishment! What is the connection, the midah k'neged midah, between the crime and the outcome?
Sometimes a person feels inspired by a great shiur or a great davening or some other positive experience. At that moment the person feels the urge to make all kinds of changes. "Konam my smartphone alay k'cheirem" -- they take a neder not to use a smartphone any more, for example "Ashkim v'ashaneh perek zeh" (Nedarim 7) -- they take a neder to add a seder of learning., for example. How long does the commitment last? Let's be real. Does it last a day or two, or a week or two? By that point the inspiration is gone and life returns to normal until the next upswing, at which point the process repeats itself.
So who is the real you? Is it the person who is inspired and wants to do better, if only the mundane morass of day-to-day life did not suck you down? Or is the real you the person who lives in the hum-drum of daily existence and those moments of inspiration are the exception to the rule?
The nafkah minah is what you give over to your children. Do you give over inspiration and idealism, even though you may not be able to maintain those height? Or do you give over the daily struggle in the jungle of corporate life, where idealism is just escapism from the work needed to make more money or earn a better position?
Explains Rav Kook, if nedarim -- if those commitments you make when inspired or in need or seeking something greater -- are not real, i.e. if your idealism is just an escape but is not part of your essence, then you cannot properly raise the children Hashem has given you. You sadly view the world backwards, and therefore Hashem c"v will take back the gift he has entrusted you with.