Start with an existing anchor
Place the walk after something that already occurs: morning coffee, lunch, the end of work, school pickup, or dinner. Stable anchors are easier to remember than a new alarm floating in an already crowded day.
Create a normal version and a short version
Decide what you will do on an ordinary day and what still counts when time or energy is limited. The short version protects continuity. It is not a punishment and does not create a debt that must be repaid tomorrow.
Reduce preparation
Keep the necessary shoes, clothing, light, or headphones where the walk begins. Choose a default route and one indoor alternative. Preparation friction feels small until it arrives at exactly the moment your motivation is weakest.
Review the week, not your character
If the routine failed, inspect the design. Was the time unrealistic? Did weather remove the only option? Was the minimum still too large? Change the system rather than treating the missed walk as evidence about your discipline.