How might even good pursuits and doing my best be futile?

Psalm 127:1-2Unless the Lord builds a house, the work of the builders is wasted. Unless the Lord protects a city, guarding it with sentries will do no good. It is useless for you to work so hard from early morning until late at night, anxiously working for food to eat; for God gives rest to his loved ones.

John 5:19So Jesus explained, “I tell you the truth, the Son can do nothing by himself. He does only what he sees the Father doing. Whatever the Father does, the Son also does.”

John 15:5“Yes, I am the vine; you are the branches. Those who remain in me, and I in them, will produce much fruit. For apart from me you can do nothing.”

Excluding God causes even our best work to be futile because our efforts have no eternal results.