I almost CONSTANTLY bite my nails...I mean like really gnaw at the cuticles, the surrounding skin and the actual nail...when I'm shopping, waiting for a bus, watching a movie, practically all the time.
They don't actually look terribly bad considering, but they often sting when I squeeze lemon or eat salty food with my hands. I have tried to break the habit many times...I've also tried that yucky stop 'n' gro varnish but had very little success with it. I even bite my toenails after I've had a bath...yep, totally minging.
I smoke when I'm having a drink in the evening...never in the house, NEVER in front of my kid...but I still consider myself a smoker and it's a disgusting habit. I also have a very high tolerance for alcyhol these days so consequently I often drink way too much without even noticing it.