Correct understanding

It is better to retreat and build a net if you are facing the abyss to envy the fish. The meaning of the whole word: facing: facing; abyss: deep water; envy: hoping to get. It means that if you stand by the water and want to catch fish, it is better to go home and build a net. It is a metaphor that only wishes without measures will do nothing good for things.

Or it is a metaphor for only hoping for something without putting the hope into action.