You are discussing the aspect of free will, and that's not the same as your purpose in life (not to mention that it didn't come from you). Maybe I'm not explaining it very well, but if you accept certain basic concepts such as the existence of a soul, the existence of a God that made the soul, and that nature is the sum of God's creation, then that leads to questions of 'why?'. Why did God go to the trouble of creating souls to populate a world that he also created?

So it's not a question of do you have control over what you do with the life that you have, even the Bible states that all of mankind has perfect free will to do as he/she pleases. The question that is asked by philosophers and holy men over the centuries is 'why are we here, what is the meaning of being alive?'

I am reminded of the story of Russian Novelist Andrei Bitov. He grew up in a communist country that actively tried to wipe all religion out. Atheism is the official 'state' religion of most Communist countries, as they want the 'State' to be the religion of the masses. When he was 27 he was riding the metro in Lenningrad (St. Petersburg) and became overcome with a great depair. He had come to the realization that existing in just the material world, in the 'here and now', in the idea that above him was no heaven, and that life under such parameters had neither future nor purpose. As he sat brooding over this thought, a phrase appeared to him (novelists are funny that way). "Without God, Life makes no sense". In his words "Repeating it in astonishment, I rode the phrase up like a moving staircase, got out of the metro, and walked into God's light."

That's a pretty powerful transformation, however, it isn't meaningful at all unless you accept that there are aspects to this experience we call 'life' that are not explained by what you see with your eyes, hear with your ears, can touch and feel with your skin, smell with your nose, or taste with your mouth. If you think that all aspects of life are covered by the biology, then that is your 'peace', but there are many people that simply can't be satisfied that the biology represents all that there is.