what happens at the end?

Does Scarlett O'Hara pull herself together and surmount another obstacle, go running into the mist, "crazed with the torture her gifts had put her to," and finally cave in, this last loss being finally too much? What happens after you win the world and lose your soul? Does she ever get Rhett back? Does she eventually turn into Blanche DuBois, the other tragic Southern Belle? Why couldn't she and Rhett live happily ever after? Vivien Leigh went through a similar relationship with Olivier, it, too, didn't last. Why? Two people who are meant to be should be finally happy, no? What went wrong?