Whoever finds their life will lose it, and whoever loses their life for my sake will find it. -Matthew 10:39
Take the case of courage. No quality has ever so much addled the brains and tangled the definitions of merely rational sages. Courage is almost a contradiction in terms. It means a strong desire to live taking the form of a readiness to die. ‘He that will lose his life, the same shall save it,’ is not a piece of mysticism for saints and heroes. It is a piece of everyday advice for sailors or mountaineers. It might be printed in an Alpine guide or a drill book. This paradox is the whole principle of courage; even of quite earthly or brutal courage. A man cut off by the sea may save his life if we will risk it on the precipice.
He can only get away from death by continually stepping within an inch of it. A soldier surrounded by enemies, if he is to cut his way out, needs to combine a strong desire for living with a strange carelessness about dying. He must not merely cling to life, for then he will be a coward, and will not escape. He must not merely wait for death, for then he will be a suicide, and will not escape. He must seek his life in a spirit of furious indifference to it; he must desire life like water and yet drink death like wine. No philosopher, I fancy, has ever expressed this romantic riddle with adequate lucidity, and I certainly have not done so. But Christianity has done more: it has marked the limits of it in the awful graves of the suicide and the hero, showing the distance between him who dies for the sake of living and him who dies for the sake of dying.
G.K. Chesterton, Orthodoxy