Many people associate the date to bad luck. Among the many explanations is that 13 is considered an unlucky number and Friday is unlucky day. Combining both compounds the bad things. There are no legitimate accepted origin however yet the fear is always there.I myself usually don't believe on myth but I developed a sort of paraskevidekatriaphobia, or the fear of Friday the 13th, because some major accidents in my life happened in a Friday the 13th. Our boarding house in college was hit by lightning on a Friday the 13th. I had my first bus accident on a Friday the 13th. In one of my trips going to work the public utility bus I was riding lost its brakes in a sharp curve and rolled over where many were injured. My wife, who was supposed to have a normal delivery got a Caesarean section for our third child on a Friday the 13th.
My explanation for this is that when people's mind whose negative vibrations merge during this particular day, it could create a negative energy that would result to unwanted events. That's why it is necessary to forget the idea and focus on the regular and normal flow of works. If in case you remember the fear, just counter it with positive thinking and prayers.
God always listens so let your fears go, and pray.