Get your food delivered straight from a farm (I subscribe to $29/week CSA for veggies and fruit, and get meat, eggs, and cream delivered once a month from SPUD. Vinegar, coconut oil, and all household items are ordered through Amazon.)
I get seduced by meat sales too, but I've found that if I get it straight from the source it is cheaper than it would even be on sale, and I can dispassionately calculate how much I'll need based on available freezer space. Stay out of the store if you can possibly avoid it and chances are you won't have to worry about this.
I also have a lot more fun when I do go to the store because all I need to get are fun things like chocolate, lox, butter, and wine (and none of those are necessities, so if I feel like I won't be able to resist temptation, I can just skip it without going hungry).