The Cynic philosopher Diogenes was once criticized by a passerby for not taking care of himself in his old age, for being too active when he should have been taking it easy and resting. As per usual, Diogenes had the perfect rejoinder: "What, if I were running in the stadium, ought I to slacken my pace when approaching the goal?" His point was that we should never stop getting better, never stop the work that philosophy demands of us. Right up until the end Diogenes was questioning convention, reducing his wants, challenging power, and insisting on truth. The Stoics agreed with his view, that old age was no excuse for coasting. In fact, we get the sense that many of the strongest passages in Meditations are written by an older Marcus Aurelius, one who is still frustrated with himself for his anxiety, for his passions, for his less than flawless record when it comes to upholding his positions. In one passage he says it more or less outright: How much longer are you going to keep doing this? You’re old and you still can’t get it right. But he wasn’t just kicking himself to feel better. He was trying to get himself to be better. He refused to take his foot off the gas. He was going to keep going right on through the finish line, and so should we. No matter how old we are, no matter how long we’ve been at this, it’s far too early to stop now, to say “close enough.” No, we are going to give our best effort. We’re going to give everything we have, with every day that is given to us...