In the house I grew up in, the fridge displayed - among some dog magnets and local pizza-joint numbers - a copy of Jack London’s credo, which I still love:
I would rather be ashes than dust! I would rather that my spark should burn out in a brilliant blaze than it should be stifled by dry-rot. I would rather be a superb meteor, every atom of me in magnificent glow, than a sleepy and permanent planet. The function of man is to live, not to exist. I shall not waste my days trying to prolong them. I shall use my time.
When I went searching for this text online, I noticed that no one was attributing it to a specific work, letter, etc. Red flag. The Jack London Online Collection at Sonoma State has done the detective work.
Bottom line: London informally wrote the first sentence. He might’ve spoken the whole credo, but all we have is an account from one reporter. “The full passage has many marks of London’s style–its directness, its rhythm, its diction–to persuade that it is authentic.”