I NEVER stepped on a crack when I was little, and I used to walk to school. The three of us would jump over all the cracks, since we didn't want our mothers to have broken backs--I'm sure we were quite a site!!!
I totally forgot about the mirror--when I was young, my mom broke one, and her and my father got divorced, which resulted in a nasty ongoing custody battle for years--she warned me never to break a mirror.
2 years ago (I'm counting), I broke one, and ended up losing a job and a boyfriend. However, since then, I have also met my husband, had a beautiful wedding, made some wonderful friends, started a job I love, and all other sorts of things.