"mission"

In the essay part of the LPI test on three days before, there was one topic about mission.
The topic was written like this, "Do you believe is there a mission on your on? If you think you have a mission to accomplish in this world, and because of it you were born, write about the mission and the reasons why you think you must accomplish it. (Do not write about going school or getting a degree. Write something specific.)"
I didn't choose this topic, but when I was thinking about this topic just about a half ago, I had one idea about "mission":
If we initially lived in heaven but chose to born in this heavy world, there should be something we wanted to do in "here", but most of us forget about it when we were born. However if someone has strong resolution for the thing, sometimes he/she could remembered a bit about the thing.
Then the people like this call the thing as mission.

For me, this assumption makes very sense rather than just believe in the mission from God. But what do you think?
Is my assumption too top-heavy?