Turn about. Unfair play.
Ever feel used, discarded, abused? Doesn't feel so wonderful, does it? Do you hurt? Feel insulted? Feel like the last breath of your faith in humanity has just been sucked out of you? Feel like someone's just used up the last bit of ability you had to build any kind of real caring or rapport with another human being? Just remember those feelings the next time you take up someone's time, get them to care for you, lead them to believe you cared about them, then throw them off like yesterday's news and insult their caring while you do it.