Did you know that it has not always been considered unlucky?
The name, Friday, comes from the Norse goddess Freya. (Wednesday comes from Odin - Odin's Day -> Wodin's Day -> Wednesday). Freya is a goddess of love, passion and self care for women.
13 is a scared number because it is the number of moon cycles within a solar year. It used to be thought that the moon governed women's menstrual cycles and that we would sync up with the phases of the moon. I have no idea if women's bodies ever did this, nowadays with so many on the pill veyr few women will be in their 'natural' cycle. As 13 is the number of moon cycles, it is linked with the power by which all life grows - plants, people etc.
So, Friday the 13th really shouldn't be considered unlucky. To those with Pagan tendancies it should be considered a holy day for women, sexual health and love.