Curses do exists. You cannot find many because they come from the heart (they are personalized). The heart can be in many states therefore giving you a desired outcome. Curses are like spells but curses last until the set goal is completed. Some have time limits to the goal. (ex: Good luck for a year.) Others work similar to this ex: I will not be happy till I find true love. Therefore putting them in a depressive state until they do. You can put a curse on yourself. You use belief, prayer, and so on. Same as any thing else. You can take them off yourself but of course it is the same process. The darker the curse the harder it will be to break especially if the curse is repeatedly said with the same intense emotions.(It requires more inner strength to free from those.) If you are cursed with a demon/angel type spirit, then that is a completely different battle. Why? Even though they can be sent to someone, they only have the power you give the spirit.
***Spells have different guidelines I can elaborate the difference if needed.
I hope I covered everything enough. The examples aren't really "true" curses (any words can be a curse it depends on how you act on it, to shape it.) but it will give you an idea of the circumstances.
Good luck with your path!