Bad habits or unhealthy lifestyle choices that people have become very accustomed to are especially difficult to change or give up. Likely an adaptation of the more common "old habits die hard." I've read all the literature, I know all the health warnings, and I'm aware of how much I spend each day on cigarettes, but still I can't resist the urge to buy another pack. Bad habits die hard. Even as a grown adult, he still bites his nails when he's not paying attention. I guess bad habits really do die hard.