I didn't actually think I was that bad - until I read this thread and it turned into a mental litany of 'Yup, do that', 'That's me', 'Uh-huh'...
Worst one is pins (and needles) in mouth - although in my defence I now am careful to use lips only (after chipping a front tooth on a pin several years ago *ahem*)
I like having lots of things on the go at the same time, so am refusing to admit that as a bad habit. LOL
And I talk to myself all the time, not just when I'm sewing. Always have. Co-workers are used to it now!!!
Bad habit I seem to be developing: turning patterns into English paper piecing because I find it easier. I started doing Sylvia's Bridal Sampler specifically with the idea that it would expand my quilting techniques since it would require learning things like foundation piecing that I haven't done before. Instead I now seem to attempt a block as intended, have it come out wonky, and instead of persevering with the 'proper' technique I convert it to paper piecing. Or if I'm feeling really rebellious I look at the instructions and go 'That would be so much easier being paper pieced' and off I go!!! LOL