What does "grass is greener where you water it" mean?

The grass is greener where you water it.

I recently realized what this really means.

"Watering" is a metaphor for giving something your attention and focus.

The grass on the other side seems greener because that is where your "attention" is going. You are "watering" it simply by "focusing" on it.

Water your "own grass," and it won't just become greener—it may become the greenest.