It's simple, really. Your character has led a hard life, but it has made them a better person and they have managed to achieve most of their goals. All the same, one night, they make a wish on a shooting star: to have grown up in a nicer, safer, happier world.
That night, it comes true.
When they wake up, it is to a life where they did not have to overcome the trials of their past.
Explain the differences in these two worlds.