A good reason to not have sex before you're married- if you and your spouse both wait, there's no way you'll be cursed with a mysterious evil force that stalks you and tries to kill you.
Seriously, great movie. With the horror genre, a movie is usually either very good or very bad, not much in between, and this was one of the few that impressed me.
An original concept that was executed well. Lots of tension and suspense throughout…