"How are you doing?"

The waiter at my favorite café just asked me “How are you doing?” and I was like “Umm, next question please.”

I just can't get used to that version of “hi”. Each time someone throws it at me my reflex is to catch it and throw it back instead of simply letting it fall. “How are you doing?” I hate that phrase because everytime I fall for it and I start to seriously consider it; the conclusion is rarely positive. The last time it was my boss who said it and I heard myself mumbling “I've been better.” I doubt he’ll inquire ever again.

When will I learn to simply say "Fine"? I guess I'm a slow learner.