Those chain letter curses are stupid and there is no real purpose to itI'd be cursed hundreds of times, because I never sent any stupid chain mail... oh wait, that's something different... I mean any stupid chain letter to any other person.
To me curses are bogus just like everything people still believe in, just because you can't scientifically disprove something that you can't prove either. The closest you'll get is something like this: If once a week you have bad luck and think you are cursed, think about all the other days you didn't have bad luck.
It's all perception and nothing more. If you believe in something, you WILL find ways to justify that.
Ones like Bloody Mary, you may not believe in it but I bet you wouldn’t do it