Is It Really Smart to Be a Smart Shopper?

In my most recent incarnation as a two-income lifestylee on one income, I've learned to shop at Wal-Mart, Target, Grocery Outlet, outlet malls, used clothing stores, and to buy things on sale. I think this is provoking overspending.

It's so cheap, I can afford it! I think floods my "Do I need this?" filter. Maybe it would be better if I bought one fine sweater for $60 rather than 6 okay ones. The thing that makes this a question, not a certainty, is that, particularly at consignment shops, it is possible to buy a fine sweater for $10. The thing is, I've got a lose grip on my wallet while I'm there. Everything is such a bargan.

Another factor. This is a real math question. It is said that you save money by stocking up on staples when they are on sale. But every month or week another staple is on sale. When is this savings realized? At death? If this week you stock up on canned tuna, and next week you stock up on toilet paper, and the following week on ketchup, and after that on your kids' favorite organic mac&cheeseinthebox...when do you get a break on your weekly grocery bill? Wouldn't I ultimately spend the same, or even less, if I only bought what I need to have on hand? Could someone run a spreadsheet for me on this one?