One trick I found really helped me curb thoughtless spending in the past was calculating the cost of purchases based not on the sticker price, but on the sticker price + whatever the compounded interest would be for the same amount of money on my mortgage. (At the time our interest rate was 5% with about 27.5 years left on our mortgage, so it effectively doubled the price of everything.) The thought was that if we spent that money vs. putting it on the mortgage, we were essentially locking those dollars in to being charged interest for the life of the loan. It doesn't take into account re-financing, etc., but it was a lot easier not to buy $10 smoothies vs. $5 ones. :-)
Thinking about interest and growth does help put prices in perspective. Using mortgage interest rates doesn't work as well these days, since they've fallen so much, but you can use the standard market growth rates instead: either 7% or 4% depending on whether you take inflation into account.
