Plans feel simpler before other people’s ordinary needs enter them.

Planning happens in a version of the world with only one person in it. On paper the day flows: leave at eight, two hours there, home by six. Then somebody needs the bathroom, a lift, lunch, ten minutes to say goodbye properly, and none of that is unreasonable; it was simply absent from the imagined version. Plans mostly fail on the humanity they left out.

When you plan anything involving other people, add a generous margin and one unscheduled gap. Ask each person what they will need. Treat the extra time as part of the plan.