Winner's Curse
Definition
The winner’s curse is the tendency of the winning bidder in an auction to be the party that most overestimated the value of the prize. Winning means you paid more than every other informed bidder was willing to, which is evidence you may have overpaid.
In practice
The RJR Nabisco auction is the textbook case: KKR won at $25 billion and spent years proving the price. The defense is discipline, setting a walk-away number before the auction starts, because inside one, adrenaline reprices everything.