Keep the direction even when the pace changes.

Pace varies with energy, season, and circumstance, and trying to hold it constant is how people burn out or quit. Direction is the thing to hold fixed. Moving slowly toward something still gets you there. Moving quickly toward nothing in particular does not.

When a slow stretch arrives, resist rewriting the goal to match your current speed. Keep the aim and let the rate drop. Check the heading monthly and the pace never, and you will cover more ground than you expect.