I was talking to my friend Jessica last night, and she was saying how she rarely drinks, and has never done drugs. Growing up she saw the effects of drugs and alcohol on her parents, and that's why she's mostly straight edge.
I learned a similar lesson with my mom's addictions. Growing up she would do an enormous amount of cleaning only to have me mess up the house again. So as an adult bachelor I'm pretty straight edged about not cleaning... I'm just going to mess it up again. That's called foresight and good time management.