Endowment Effect

Once you touch something, you mentally own it. This is the endowment effect — you value things more simply because they're "yours." Free trials, test drives, and Amazon's free returns all exploit it: once the box is in your house, you're far less likely to send it back.

Studies show people often demand twice as much to give up an item as they'd pay to buy it. That's why stores want you holding the merchandise. That shirt on the hanger? Meh. That shirt in your hands at the mirror? It already feels like yours. Awareness of this bias is your best defense.