It doesn't bother me at all but if something did happen, I would blame the day. IE if my kid peed her pants, it would be Friday's fault, not potty training.
This made me Lol. I was also very superstitious. My Nanny and my Abuela made me that way. I have to convince myself that it means nothing at all. I was excited this year though since Sophie's 3rd birthday was Friday the 13th. But now that I think about it, she got lice and we had to spend her birthday at home combing nits out of her hair for over 2 hours.