The way to live a long time—oh, a thousand years or more*—is something between the way a child does it and the way a mature man does it.
Give the future enough thought to be ready for it—but don’t worry about it. Live each day as if you were to die next sunrise.
Then face each sunrise as a fresh creation and live for it, joyously.
And never think about the past. No regrets, ever.
— Robert A. Heinlein,
(*In the book the character who speaks this line is essentially immortal.)