Losing something hurts more than an equivalent gain feels good.
Losing $100 hurts more than finding $100 feels good. Loss aversion describes that asymmetry. The pain of losing something weighs more heavily on our decisions than the pleasure of gaining the same amount.
That's why it's so hard to sell a stock that's down, even when it's the most rational decision. Investors tend to hold onto positions that already lost value for longer than they should, hoping to "avoid locking in the loss," while selling positions that gained value too quickly.
In their prospect theory, Kahneman and Tversky showed that we value losses substantially more intensely than equivalent gains, an effect that later studies estimated at roughly a factor of two. That asymmetry explains a good part of our risk aversion, even when information is complete.
Source: Kahneman, D. & Tversky, A. (1979). Prospect Theory: An Analysis of Decision under Risk. Econometrica, 47(2), 263-291.
Framing a benefit as "don't lose your discount" usually moves the decision more than framing it as "gain a discount," even though both describe exactly the same thing. It's one of the most used, and most underestimated, levers in pricing and retention.
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