[Tiva]

Okay
I did set it up to where an earth nation guard was missing. They could find you after you accidentally show off your fire bending. Or your parents could send for them. Same thing with the White Lotus if you want. You could also just decide that it is time to leave via a spiritual message in your dreams from the past avatars.
If you want to do the past avatars one I can write out a pretty encompassing statement for it.