A daily shower.

"People often say that motivation doesn't last.Well neither does bathing - that's why we recommend it daily." - Zig Ziglar

Motivation, prayer, exercise, goal reflection... and bathing.... are all the same. To go one step further than Zig, a day without a shower won't kill you, and with some deodorant people may not even notice. There are some who even recommend that you not bathe daily. But each day you don't bathe the dirt and grime and odor compound. You don't know when the tipping point is, but one day you wake up laying in filth with rats keeping their distance from you.

Motivation, prayer, exercise and goal reflection are the same. A day missed may even be a good thing. But a day missed makes the next day easier to miss, and so on and so forth. The next thing you know you are completely unmotivated, disconnected from God, out of shape, and drifting through life.

The analogy breaks down when you get to the recovery part. Months without bathing can be rectified within a day or two. Months without motivation, prayer, exercise, or goal reflection take much more work to recover from.