Bad tippers are annoying, but they are the minority.
Awesome tippers are awesome, but they are equally a minority.
Most people are average tippers. On a given night I can pretty much guess how much money I made based on how busy I felt I was because, in general, most people tip the same way, and the shitty tips tend to get canceled out by the awesome tips anyway.
The one instance where bad tips are
extra irritating is when you are waiting on a large group of people with a very large tab, and they don't tip accordingly.
Overall, though, I've gotten over it. I tip like a crazy person because I am in the industry and that's just what we do.