It didn't matter what got the other going, really. Anger, sadness, just hunger in general? It usually all lead to the same result most of the time which was feeding off someone. Thankfully most learned quick how much to take if they didn't want their meal of the moment to keel over, to be caught or any manner of other things really.
Of course, while Em hadn't noticed any of those things? Damon did. And being older, also meant he was stronger. The second the guys heart beat started to wane slightly, fingers curled around the youngers shoulder, forcefully hauling him backwards. Grip strong enough to keep the younger from shrugging him off as well. "Enough." He hissed, tone sharp. Enough to make it obvious he was charge in case the other went full on his instincts to struggle back. "You hear his heart? That usually means stop"And if he didn't, then Damon would make him.