Charles H. Spurgeon on Psalms 119:143

Trouble and anguish have taken hold on me. This affliction may have arisen from his circumstances, or from the cruelty of his enemies, or from his own internal conflicts, but certain it is that he was the subject of much distress, a distress which apprehended him, and carried him away a captive to its power. His griefs, like fierce dogs, had taken hold upon him; he felt their teeth. He had double trouble: trouble without and anguish within, as the apostle Paul put it, "without were rightings and within were fears."

Yet thy commandments are my delights. Thus he became a riddle; troubled, and yet delighted; in anguish, and yet in pleasure. The child of God can understand this enigma, for well he knows that while he is cast down on account of what he sees within himself he is all the more lifted up by what he sees in the word. He is delighted with the commandments, although he is troubled because he cannot perfectly obey them. He finds abundant light in the commandments, and by the influence of that light he discovers and mourns over his own darkness. Only the man who is acquainted with the struggles of the spiritual life will understand the expression before us. Let the reader herein find a balance in which to weigh himself. Does he find even when he is begin with sorrow that it is a delightful thing to do the will of the Lord? Does he find more joy in being sanctified than sorrow in being chastised? Then the spot of God's children is upon him.