Be forced to acknowledge and accept an unpleasant consequence of your action. The full expression is “Who pays the piper calls the tune,” which is to say that money calls the shots (“Money makes the mare go” is the same idea). But although a request can be melodious, the phrase came to have an unpleasant connotation, as if the music that the piper produced was not what was anticipated. For example, you tell your supervisor and your colleagues that you can undertake and finish an important assignment in two days, but you can't. As your supervisor takes you to task, you silently admit that you bit off more than you could chew—you're paying the piper.