When you try to live frugally, you basically abide by few of the principles:
1) Don’t buy the stuff that you don’t need.
2) Buy the stuff that you need at the lowest most prizes.
To keep up with the second one, how many times you go to a sale or wait for one. But has this ever happened to you that shopping from sale turned out to be even more disastrous? There is more then one way this can happen:
1) I go to a sale and find that deal is something like, buy 5 KGs of ABC and get 1 KG free. Assume I generally consume only 1 KG of such stuff but the temptation to get one KG free will force me to buy 5KGs. Result, chances are quite good that half of the stuff will be spoiled before I can use it or I need to put in more money to store it.
2) Deal is to buy stuff ABC and get XYZ on a discounted price. I need XYZ and don’t need ABC. Still I will be tempted to avail that deal. Result, I actually not saved through discount, rather spent extra by purchasing something I don’t want.
3) You went to buy stuff ABC and found stuff XYZ has a great deal on. You know you can do without XYZ but deal is unbelievable. You end up buying XYZ and wasting money.
That’s why I always say that sales are absolutely anti frugal. They basically want you to spend more rather then giving you good deals.