Pyrrhic victory

A Pyrrhic victory is one where your own losses or damage make it nearly as costly as defeat.

Perhaps that business rival finally went out of business after you lowered prices so much that you can now barely get by. Maybe you managed to prove you were right at the cost of ruining a relationship. Or it could be that the kids did in fact get in the car and go out on that blasted walk only for everyone to have a miserable time, angry at each other for the rest of the day.

Or maybe, as King Pyrrhus of Epirus found in 279 BCE, you won several battles against the Romans while losing so many of your best warriors as to make you wonder at the worth of the whole campaign.