How can we pay the thanks for each limb of our body? When we see the ill and crippled in hospitals or when we are ill we can understand how valuable health is and how can we pay the thanks due for our health? The worship which God Almighty orders us to do is in fact for our benefit for our spiritual refinement and a good personal and collective life. Furthermore if we believe in and worship God. He will reward us with infinite happiness and bounties in an external world in Paradise.
In sum we see that almost everything we have is given to us for nothing our part in the bounties we enjoy in the world is quite negligible. Like this the will power we have is equally negligible when compared to the consequences which God Almighty creates as a result of our use of it. However weak it is and however difficult it is to understand its true nature. God creates our actions according to the choices and decisions which we make through our will power.