Spilled Drinks and Dirty Looks

Tonight at work was particularly hectic with a new batch of college kids looking for a place to celebrate their spring break. I tried my best to manage the crowd, but I couldn't keep up with everyone's orders and soon enough, there it happened, I accidentally knocked over a glass of red wine onto one of our regular customers' white shirt. He gave me that look, you know, the 'how could this happen at my favorite bar?' kind of glare. Now here's where things get interesting: after cleaning up the mess as best as I could, and offering to buy him another shirt, he stormed out of the place with his buddies in tow, leaving a big empty spot on the bar that no one else seemed interested in filling. It was an expensive lesson in customer service, but here's my question: how do you handle awkward situations like this without losing your cool? I'm curious to hear what others have experienced and how they've handled similar mishaps.