I told a fairly obnoxious and (in my mind) idiotic customer to "take a chill pill" on a conference call. This did not work out well. I did call them back and apologized before my management told me too, but I'm claiming no credit there, that was just pure self-preservation kicking in. On the plus side, after that day, I (slowly!) started to understand how salespeople can be really, really good at a really, really hard job. I very much enjoy sales now and I think I have a lot more empathy for where my customers are coming from thanks to that very dark day.