Too bad balance is not one of my strengths

I read this selection from The Weight of Glory (C.S. Lewis) the other day and have been thinking about it a lot:

The war will fail to absorb our whole attention because it is a finite object, and therefore intrinsically unfitted to support the whole attention of a human soul. In order to avoid misunderstanding I must here make a few distinctions. I believe our cause to be, as human causes go, very righteous, and I therefore believe it to be a duty to participate in this war. And every duty is a religious duty, and our obligation to perform every duty is therefore absolute. Thus we may have a duty to rescue a drowning man, and perhaps, if we live on a dangerous coast, to learn life-saving so as to be ready for any drowning man when he turns up. It may be our duty to lose our own lives in saving him. But if anyone devoted himself to life-saving in the sense of giving it his total attention --so that he thought and spoke of nothing else and demanded the cessation of all other human activities until everyone had learned to swim -- he would be a monomaniac. The rescue of drowning men is, then a duty worth dying for, but not worth living for. It seems to me that all political duties (among which I include military duties) are of this kind. A man may have to die for our country: but no man must, in any exclusive sense, live for his country. He who surrenders himself without reservation to the temporal claims of a nation, or a party, or a class is rendering to Caesar that which, of all things, most emphatically belongs to God: himself.