Phrase used when someone shoots you down or causes slight disappointment. Used sarcastically, or to break tension.
Joe: Yo man, where's the last slice?
Steve: Ah sorry dog, I ate it.
Joe: Why you gotta shit on my heart man?
Past-Tense:
Joe: So dude, what happened with you and your girl last night?
Steve: Sorry man, she shat on my heart, I wasn't havin' that.