Changing circumstances.

This is a very common manipulation in sales and business. I won't beat around the bush, you'll see the example right now. During a presentation, you are suddenly told that your competitors have a better offer, but if you change your mind now, the deal will happen. They can also offer you a bonus, or reduce the price a little, but tell you that you have to make a decision here and now. The remedy is very clear: don't make hasty decisions or conclusions, and always remember that you are probably being manipulated.