You have to eat, right? As long as you're not wasting a bunch of food, eating a very poor diet, or buying high end crap that is simply for convenience, I don't think any face-punching is in order. Spend money on what you want, just try to want less as often as possible. That includes food, but only to a certain extent.
If the grocery budget is really "eating" at you, consider slightly smaller portions, or cheaper nutrients like beans, eggs, oils, or try making more from scratch. On the portion size thing "hedonic adaptation" is applicable, meaning your body will adjust. The less you eat, the less hungry you will be, and vice-versa. Try it out, it works. Just make sure you get enough nutrition.
I've been fairly successful limiting my desires, but I receive a lot of collateral benefits (like the opposite of collateral damage) from my work and my wife, so most of my desires are met for me without having to spend much.