And the best way to do that is to set long-term goals and get to work on them. The most important one is this: A year from now, you should be able to do long and slow aerobics (that’s breathing hard but still able to talk; it’s 60–65 percent of your maximum heart rate) for, say, three hours without getting exhausted. You should be able to do that in your sixties, seventies and eighties . . . and a variation of it in your nineties. That’s an all-morning bike ride or a hike at a firm but not punishing pace. You should do something like that, oh, once a month. Two hours is okay some months, but
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