Triskaidekaphobia is a morbid fear of the number 13.
Like all phobias it can be treated by systematic desensitisation - gradual and progressive exposure to the thing you fear most. In the case of Triskaidekaphobiacs this is usually done by getting them to first look at a number 7, then feel one, then hold one for a while, until they feel confident enough to carry a number 7 around in their pocket. The process is repeated with the numbers 8, 9, 10, 11 and 12, before they move on to tackle the Big One.
OK, OK: I made that up. It's probably true though. Um.....?