Oswald Chambers says:
Fussing always ends in sin.
We imagine that a little anxiety and worry are an indication of how really wise we are; it is much more an indication of how really wicked we are. Fretting springs from a determination to get our own way. Our Lord never worried and He was never anxious, because He was not "out" to realize His own ideas; He was "out" to realize God's ideas. Fretting is wicked if you are a child of God.... All our fret and worry is caused by calculating without God.
-from My Utmost for His Highest