As Doyle says, it doesn't cost you anything to follow a silly superstition (as long as it's not directly gameplay related, like "I always push with 72o" or something!).
Anyway, re: the original post, as with a lot of decisions in poker, it depends. If you're still confident you're playing your 'A' game, then you have little to lose by playing through a bad run. After every session, review the hands you've played and look for any leaks. Yes, you may be having a bad run, but you may also be contributing to it through poor play in certain situations.
If you are playing poorly as a result of a bad run, take a break. If you can't let poker go completely in the interim, pick up a book or go and donk around at play money tables for a few days or something. I recommend just breaking off completely for a while though. Once you feel refreshed, go for it again.