It's funny how many people dismiss this type of belief.
The human mind is a powerful thing,in many cultures where a belief system is so strong and ingrained from a very young age,black magic,voodoo,and many other types of unexplained phenomena does exist....to a point.
if you have such beliefs,and someone put a "curse" on you,your mind would make it very real.Take so called miracle curses.The mind plays a huge part in curing the body.You hear stories of people having uncurable cancer and other illnesses that just disappear.A lot of people may be very positive and really try to get through a terminal illness,but the word "cancer can work the opposite way.You may believe that the treatment you are getting will fix you,but subconciously,as soon as you hear the word cancer you think "shit,im going to die".Where other people really believe that they will be cured and have some sort of alternative treatment.This may just be a placebo physically,but mentally,the mind believes it will work so it does.
Same thing with voodoo and black magic,if a person's beliefe in it is strong enough,they can make the curse a reality.And I'm not talking about what you see on TV,like the movie thinner,I don't believe a curse can be out on a person without their knowledge.That is the whole point of a curse,you do it their face to make them fear it.
Education can't cure generations of culture and a deep seated belief system.Many people do things out of custom,but a lot of them actually really believe what they are doing.Thi is what makes it very real in their minds.