The Bible does tell us who we are and what we should do, but it does so through the lens of who God is. The knowledge of God and the knowledge of self always go hand in hand. In fact, there can be no true knowledge of self apart from the knowledge of God. He is the only reference point that is reliable. So, when I read that God is long-suffering, I realize that I am not longsuffering. When I read that God is slow to anger, I realize that I am quick to anger. When I read that God is just, I realize that I am unjust. Seeing who he is shows me who I am in a true light. A vision of God high and lifted up reveals to me my sin and increases my love for him. Grief and love lead to genuine repentance, and I begin to be conformed to the image of the One I behold.
If I read the Bible looking for myself in the text before I look for God there, I may indeed learn that I should not be selfish. I may even try harder not to be selfish. But until I see my selfishness through the lens of the utter unselfishness of God, I have not properly understood its sinfulness. The Bible is a book about God. As Moses would learn during the Exodus who he was bore no impact on the outcome of his situation. Who God was made all the difference.