Why do I buy things I don't need just because they're on sale?

You did not plan to buy this. You saw a lower price, and your hand moved before your reason could ask a single question. This happens again and again, until the cupboard is full of things bought for their price, not for any need of yours. Add up all these bargains, and you find you spent more than if you had bought nothing at all. Ask yourself plainly: who is served by this sale? Not you — you did not know you wanted the thing an hour before you saw its price. The seller is served. The store's plan to clear its shelves before the season ends is served. Reason, if you use it, is not moved by a smaller number when the real question is whether you wanted the thing at all. This is not a flaw in your character. It is a habit of the eye and the hand, formed by looking at prices before looking at needs. Reason can be trained to ask the right question first — and this is a thing you can practice, plainly, starting with your very next purchase.