"I'm too tired"

The last objection before the social ones is the one you'll have at half past five. You're tired. The walk is one more thing. The car is the kind option.

There's an old study that speaks to this directly, and I'll describe it carefully because it's small. Robert Thayer, in 1987, had eighteen volunteers, on twelve separate days, either eat a chocolate bar or walk briskly for ten minutes, then rate their energy, tiredness and tension over the following two hours while going about their day. The walk raised energy and lowered tension, and the effect lasted the full two hours. The chocolate bar raised energy briefly and then, an hour later, left people more tired and more tense than before. Eighteen people is not many, and the study is nearly forty years old. But it's the plainest test I know of the belief that tiredness is a reason not to move, and it found the reverse.

The reason, I think, is that most of the tiredness at half past five is the tiredness of a still day, and stillness isn't cured by more stillness. It's cured by a change of state, and a ten-minute walk is the cheapest change of state there is. There's a book in this series about the chair and what a day in it does, and it's named in the notes. Here I'd only say that the tired feeling at the end of a day at a desk is a poor guide to what your legs can do, and that the walk home, or the walk to the shop before dinner, is the thing most likely to end the tiredness rather than the thing most likely to deepen it.

Try it once at the worst time. When you're most tired and the keys are in your hand, walk the half mile instead, at the talking pace, and notice how you feel at the far end. Not at the start, where the objection lives, but at the shop door. In my experience most people feel better there than they did at the hook.