I just happen to watch Evan Almighty. It is story out of the bible.  But the underlying concept is real magical. It conveys a few very strong beliefs which drive this universe. Most of the times in life we do not understand why things happen the way they do, sometime we do not know why we do what we do. We almost do things like someone is instructing us with a stick in hand. But some how every thing seems to have a purpose. In fact all religions teach the same concept. The essence of Bagvat Gita, where Lord Krishna preaches Arjuna reflects the same thoughts

• Whatever happened was good.
• Whatever is happening is also good.
• Whatever will happen that also will be good.
• What did you lose that you are crying for?
• What did you bring which have you lost?
• What you created that is destroyed?
• Whatever you have taken is taken only from here
• Whatever you have given is given only from here.
• Whatever is yours today will belong to somebody tomorrow
• And belong to someone else day after tomorrow.

This inevitable change is the law of the universe
And the objective of my creation.
-BHAGAVAN SREE KRISHNA

In the movie a Congressman, gets instructions from God to build a Ark ( a large ship).  He tries to question, the entire world laughs at him.  But God gives him no other alternative; he has to build the Ark within a specific period of time.  After initially rebelling, he surrenders and decides to do what God says… it is a Hercules task and he has no clue how to go about.  Got says “your job is to do… for doing ask and you will get”.  Once he decides he will do help and support come from all unexpected quarters.  He finally finishes the Ark only to realize later that he is going to save all living things from getting washed away from floods.
There is a purpose in every doing… which is unknown to the doer.   By the time the purpose gets unearthed the doing gets forgotten.