Promise Of Our Past

The story between two ill fated lover, who destined to be not together. They were strangers in the future, to avoid repeating the history. They just gonna cause each other pain, however they made a promise from their past which could lead them to find each other again in the future.

What will happen to them?
Will they gonna let go the past and just focus on their new life?
Or they are gonna fight again until the heaven will give them the will to be together.
Are they going to have an happy ending? Or a repeated painful past?