I have lost count of the number of questions I've seen recently saying things like, "What is the cure for an illness caused by witchcraft?" or "So-and-so put a curse on me! How do I break it!?"
First of all, if you're like 12 years old, it's HIGHLY unlikely that anyone cursed your ass! THAT level of skill (being able to not only perform a curse, but have it work correctly and LAST, etc.) takes a LOT of time to master. Your 13 year old "BFF" didn't curse you, even if s/he said so. More than likely, the people who would have the skills to do it aren't going to care enough about you to curse you, or they're going to care more about their own karma to not do it, no matter how irritating you may be.
If you think you're getting sick, you'll get sick. Hypochondriacs do it all the time. The same is true for curses and all that crap. If you BELIEVE you were cursed, you're going to start experiencing "symptoms" of that curse, but it isn't because you WERE cursed. The power of suggestion is a powerful thing.
I could have waved my arms at some of the people in my school back in high school and then pointed at them and shouted, "I CURSE YOU!" and then when they tripped trying to run away, they would have believed it was part of their "curse" and would have started experiencing other "symptoms." It wouldn't be because they were actually cursed, though, it would be because they believed they were and began to manifest those thoughts.
This is sort of tied in with the whole positive affirmations thing. If you believe something is true, it becomes true.The human mind is very powerful and capable of a lot more than people give it credit for.