I found it interesting that my brother opened his answer to this question with a dictionary definition of superstition, being the belief that a certain action will cause a certain event without an actual direct cause and effect link.
But then again, this word was invented, and its definition was written, by people of a culture whose belief in magic is nil, and whose belief in religion is minimal. So perhaps it is not surprising that such things are dismissed as being superstitions.
But, look at it from another angle. What if magic is real? What if the Gods are real? Who is to say "there is no direct causal link" between a certain action and a certain result. The Valar can ALWAYS be the link, they may intervene at any time, and if they suddenly decide that the number 13 is unlucky, and anyone who answers a prompt in a certain community bearing the number 13 will have eternal bad luck, then so be it.
Yesterday my brother and I received an email (now if anything is evidence of a missing link between cause and effect then anything to do with computers is certain to be just that), which threatened that if we did not pass on the email to ten friends then we would die, just as some poor woman did who failed to do the same. Maitimo merely laughed and pressed the "delete" button, and reminded me that the threat of death only works on mortals.
My point though, is that magic, and superstition, and anything of that nature, is really nothing more than a science which is not yet understood. A computer in Valinor would have been called Magic. A gun would have been called the work of Morgoth. Here, in the Seventh age of Arda, they are merely scientific tools of one sort or another, and no-one regards either of them as magic.
Character: Maglor
Fandom: Silmarillion