1. You are not your size.
Smaller size can always be justified by the fact that you lose weight and you will definitely be able to "fit into these jeans", and the dress that sits on you freely can really be adjusted in the atelier.2. You buy defective items.
Due to minor defects, shops give significant discounts on some items.
It turns out that a woman has to immediately carry a new thing to the dry cleaner or to the tailor. Are you sure that clothing repairs will not cover that very discount?
3. You take things that you don't need.
Discounts work on people in a magical way, forcing them to take even what they don't need. It's profitable! Going to a sale without a must-have list can lead to the purchased items being irrelevant to you.4. You buy things that you haven't worn before (and you hardly will).
Sales are not the best place to experiment with style, you can opt for extravagant items at attractive prices, without thinking that such a style absolutely does not appeal to you in everyday life.
It will be interesting for you to read, how not to lose your head on sales?