I found the Book of Tobit interesting enough to writeRaphael In America in part because of how Tobiah's life is most obviously shaped by other people's choices. He's definitely not purpose driven. In fact, should he have gotten into a purpose mentality, he'd quite likely sit around arguing with Dad about how he should go do whatever his purpose is instead of travelling or whatever.
There are two views by which we can see Tobiah. He is in a family in the Middle East, and as such he is expected to fulfill certain obligations, which he does. In another sense, we can see a series of events, which other actors do, that directly effect Tobiah's life. Tobit and Sarah both pray for death, God sends Raphael, Raphael guides Tobiah. Tobiah doesn't look for a global purpose or meaning at any particular scale; he just does what the others ask him to do.
This is why there are a lot of people in the world who will never walk around with the confidence of some specific purpose in their lives. It is merely arrogance to assume I could know, with any clarity, a purpose- unless, of course, you define purpose so broadly as to be meaningless. At that point, I fear it becomes an excercise in word magic, with people trying to eradicate any mention of uncertainty in order to generate the illusion of certainty.