Same walk every night with the dog means you notice how your mood changes even when the route doesn’t.

Holding one thing constant is what makes everything else measurable. If the route never changes, the only variable left is you, and the difference between Tuesday and Thursday becomes obvious. People reach for new experiences to understand themselves, when a repeated one is often the better instrument.

Keep something in your week that does not change and let it work as a gauge. The same walk, the same bench, the same ten minutes before bed. On the nights it feels long or heavy, that is information about your week rather than about the walk.