Starving eternally

It is not simply that God has arbitrarily made us such that He is our only good. Rather God is the only good of all creatures: and by necessity, each must find its good in that kind and degree of the fruition of God which is proper to its nature. The kind and degree may vary with the creature's nature: but that there ever could be any other good, is an atheistic dream. George Macdonald, in a passage I cannot now find, represents God as saying to men, 'You must be strong with my strength and blessed with my blessedness, for I have no other to give to you'. That is the conclusion of the whole matter. God gives us what He has, not what He has not: He gives the happiness that there is, not the happiness that is not. To be God - to be like God and to share His goodness in creaturely response - to be miserable - these are the only three alternatives. If we will not learn to eat the only food that the universe grows - the only food that any possible universe can ever grow - then we must starve eternally.

C.S. Lewis, The Problem of Pain, Ch.3 Conclusion, (pp. 47)

Here is a profound insight into happiness and the nature of sin. When we sin, we participate not in the life of God, but in disorder and nothingness. God creates this universe and He also sustains it: everything that is not of Him is essentially nothing, doomed to disappear into the void. This is I think in a very real sense what Hell is: total lack of true being.

We must learn to do only God's will because in reality that's the only thing there is to do. Any time we deviate from God's will we participate in a life that is doomed to nothingness, that is, to death.