Jack London said this quote

He was mastered by the sheer surging of life, the tidal wave of being, the perfect joy of each separate muscle, joint, and sinew in that it was everything that was not death, that it was aglow and rampant, expressing itself in movement, flying exultantly under the stars.

~ Jack London

There is an ecstasy that marks the summit of life, and beyond which life cannot rise. And such is the paradox of living, this ecstasy comes when one is most alive, and it comes as a complete forgetfulness that one is alive. This ecstasy, this forgetfulness of living, comes to the artist, caught up and out of himself in a sheet of flame; it comes to the soldier, war-mad in a stricken field and refusing quarter; and it came to Buck, leading the pack, sounding the old wolf-cry, straining after the food that was alive and that fled swiftly before him through the moonlight.

~ Jack London

Do you know the only value life has is what life puts upon itself? And it is of course overestimated, for it is of necessity prejudiced in its own favour. Take that man I had aloft. He held on as if he were a precious thing, a treasure beyond diamonds of rubies. To you? No. To me? Not at all. To himself? Yes. But I do not accept his estimate. He sadly overrates himself. There is plenty more life demanding to be born. Had he fallen and dripped his brains upon the deck like honey from the comb, there would have been no loss to the world. The supply is too large.

~ Jack London

He had no conscious knowledge of death, but like every animal of the Wild, he possessed the instinct of death. To him it stood as the greatest of hurts. It was the very essence of the unknown; it was the sum of the terrors of the unknown, the one culminating and unthinkable catastrophe that could happen to him, about which he knew nothing and about which he feared everything.

~ Jack London