Sometimes I buy things solely to avoid shopper's remorse.  Not buyer's remorse, where you buy something and wish you didn't, but shopper's remorse, where you think about buying something, decide against it, then regret that decision.  It usually happens when I'm in the market for something and actively tracking the prices, only to see a price drop and not jump on it.  Sometimes it's just not the right price, or it's not the right time.  If I decide not to buy it, I'll often keep thinking about it for a few days, until I'm forced to go back to the store or website and see if it's still available at that price.