Fitness is partly preparing for ordinary tasks you hope never become difficult.

Much of fitness has nothing to do with performance. It is about keeping ordinary things ordinary: carrying luggage, playing on the floor, walking a long way without thinking about it, recovering from an illness quickly. These are the tasks you hope never become events, and they become events silently when the underlying capacity is allowed to slip.

Train for the ordinary rather than for a number. Ask what you want to still find easy in twenty years and work backwards from that. It is a more durable motivation than most.