repeat after me paraskevidekatriaphobia. This is the learned name for fear of Friday 13th. It doesn't trip off the tongue quite as lightly as triskaidekaphobia, which means fear of the number 13. The longer tongue-twister is derived from the Greek words for "Friday" (Παρασκευή), "thirteen" (δεκατρείς), and "fear" (φοβία, from φόβος). But don't blame the ancient Greeks, The term was made up just a century ago, when scientists and psychologists still knew Greek and Latin.
If you're nervous about Friday 13th, here's my suggested remedy. Try to memorize and repeat 13 times (without looking) the word paraskevidekatriaphobia. By the time you get this right, Friday 13th will be over.
Friday 13th has generally been a lucky day for me, but then I'm a contrarian. As a student of practical superstitions, I'd be interested in your experiences of Friday 13th, in the past and on the morrow.