Normally, curses are null and void unless the person who cursed you has legitamate authority over you. You can find examples in history and I think even a gray book by TAN called "The Catechist" where parents curse their children and such misfortunes really do befall them. However, attending the Holy Sacrifice of the Mass and wearing the Brown Scapular also gives protection against these things, like hexes and wichcraft curses, etc.

On another note, you can retort with "And may you go to Heaven". Jesus said "Bless those who curse you". And Marcus Aurelius says the best revenge is to just be happy and not act like the other person. Rather, we should feel sorry for them because they are not happy with their life.
  Of couse, there is always the possibility you did/said something to aggrivate them and provoked that response...

I have not heard it told to me in years. In my culture, it is followed by fisticuffs if the person is a fighter. In my experience, anyone that told me to go to hell was a barking dog with no bight, so it was not necessary to get the first punch in. 

A diplomat is someone who can tell another person to "Go to He**" and that person will actually look forward to the journey.







(joke)