I've always believed that I had unusually good luck when it came to dice games. It turns out I just always picked 7, which is the most common number.
I sort of still believe in the one about 7 years bad luck for breaking a mirror. I broke a mirror once when I was 10. After that, I went through high-school, which was pretty crappy. Then I went to college which rocked.
I never believed much in Friday the 13th being any sort of unlucky sign.