My last table last night was two women who'd spent the day doing Christmas shopping. They ordered two mega sized hurricanes and two shots of Crown Royal; then they ordered our dinner promotion that includes an appetizer, and they threw on some extra stuff. The hurricanes were $7.25 each, and the Crown shots $7 each, so even with the promotion their bill ended up being $55. At my restaurant, that's sort of a lot for two people, so I was prepared for complaints.
After I delivered the bill, I saw them scrutinizing it, going over each line--usually a very bad sign. I was running the carpet sweeper, and as I came up the aisle I overheard one of them basically say that yeah, they ordered expensive drinks, so that was right. When they put out their credit card, they did so with a smile and a thank you. There were no grumblings, no bitching, no shady comments about "boy, those drinks sure are expensive! (STARE)".
That is how you behave when you overspend! It's nobody's fault but your own, and it's certainly not your server's fault. (I did suggest the larger sized drinks, since they said they needed alcohol, but that's only $2. They came up with the Crown shots, and the meal add-ons, themselves.) I was so relieved after the day I'd had that I snagged the manager's card and gave them a 10% discount--I told them it was the "only non-cranky customers all day" discount, which was also true.