"Half done is better than not started"

By five o'clock you had six things under way, and there's comfort in that. Nothing has been neglected, and every one of them has had some attention. It seems better than finishing two things and not touching the other four.

I don't think it is, for three reasons. The first is simple arithmetic, and you can check it.

Suppose you have three tasks, each needing two hours, and six hours to do them in. Do them one after another and the first is finished at the end of hour two, the second at hour four, the third at hour six. Now do them in rotation, half an hour at a time. The first is finished at five hours, the second at five and a half, and the third at six.

The total work is the same. But in the first case two of the three were delivered hours earlier, and someone could be using them. And I've assumed switching is free. Add the restart costs from chapter 4, a dozen or more of them, and the rotation no longer fits in six hours at all. If the day ends at hour five, the person working in order has two finished tasks and one untouched. The person rotating has three unfinished ones.

The second reason is that a half-done task has usually delivered nothing. Half a report can't be read, and nobody can use a reconciliation that stops at row forty. The shelf with two holes drilled doesn't hold books. Most tasks pay out only at the end. Until then, the hours you've put in are an investment with no return. So the six things you had under way at five o'clock were really six investments, and none of them had paid anything yet.

The third reason is that open tasks take up room in your head. E. J. Masicampo and Roy Baumeister showed this in a series of studies. They gave people a goal and left it unfinished, then had them do something unrelated. The unfinished goal kept intruding. People had stray thoughts about it while they tried to read, and they did worse on an unrelated word puzzle. Each item in the pile does this to you, which is why "Ring Dave back??" floats up while you're trying to write about budgets.

The same studies found a way out that doesn't require finishing everything, and the method in chapter 17 depends on it. When people were allowed to make a specific plan for the unfinished goal, saying when and how they'd do it, the intrusions stopped. Their minds let go of it as though it were done. So the mind seems to need to know that an open item is taken care of, and a concrete plan is enough for that.

None of this means you must finish every task in one sitting. A report takes days. It means that at any given time you want as few things open as possible, and each one properly parked.