As the psalms begins we are told that there are two types of men: 1.) those who delight in the law of the Lord and 2.) the ungodly.
Notice that the godly man is describe in 3 way. FIRST - What he does not do: He doesn’t walk, stand or sit with the ungodly, the sinners or the scornful. These corrupt good morals rather than promote them.
SECOND - In order to build good qualities the godly man is described as delighting in and meditating on God’s law. He does this day and night.
THIRD - This man is secure and fruitful. The tree planted be the water never lacks for sustenance and has shelter. In much of Palestine (like the western parts of this country) the land is arid and rough. But down by the streams and water courses there are massive stands of trees. This is where the biggest and most fruitful trees are because of the abundance of water, and since water runs to low places, the trees down in the river bottoms are sheltered from the wind. So in the deserts of life, the godly man is a massive, well watered and sheltered tree. Truly he will “prosper in whatever he does.”
But what of the ungodly man, the sinner? He has no stability or fruitfulness at all. He is chaff - the dry, useless husk driven by the parching winds. He cannot last, the cannot stand. He cannot have his works judged, for then nothing would be left.
So one will stand mightily, another fall completely.