Knowing your "God given purpose" is something no one should worry about. There is nothing in the Bible that advocates knowing or seeking our purpose in life. Whatever happens in our life just happens. It just comes to pass without us knowing what it is. Plus, the things in this life are only temporary, not eternal. God has specific thoughts towards us and only he knows our expected end (Jeremiah 29:11).
There are two types of wills of God laid out in the bible: 1) God's sovereign will and 2) God's will of command. God's sovereign will is something we cannot control, change, or know. If we try to know His sovereign will, why things happen, what will happen, and when things will happen in our lives, then there would be no need for hope or faith. If we knew everything such as our purpose in life and what we will do in the future, there would be no need to have any hope or faith.
Now God's will of command is what God commands us to do. We can either succeed or fail in this action. You know how Jesus said in Matthew 7:21, "Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven."... if we want to enter the kingdom of Heaven, we must do the will of the God. And the will of God is laid out here in this verse:
Romans 12:1-2
I beseech you therefore, brethren, by the mercies of God, that ye present your bodies a living sacrifice, holy, acceptable unto God, which is your reasonable service. And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God.
That is what I would say our purpose in life should be...to be a living, holy, acceptable sacrifice unto God, not conforming to this world, and being transformed by the renewing of our minds.