We can infer that the psalmist is someone who has been blessed by God. The principle in this psalm, then, is that all human effort is vain unless we have the Lord's blessings. That means that we have to take active steps to involve Him in every aspect of our lives. This lesson is applied here to four areas of life: 1) building a house, 2) guarding a city for security issues, 3) working long hours, and 4) rearing the children.
The psalmist also mentions sleep, which symbolizes and suggests the setting aside of care and forgetting one's need. Those who put their trust in God are delivered from fretting and fuming, and they are supplied rest. They sleep secure. They are not at all worried and overwrought. We can relate to sleepless nights because we have all been in a state of anxiety about something.
This is even mentioned in the New Testament about Jesus, when the disciples were sailing across the Sea of Galilee, and the boat was pitching about wildly in a storm. Jesus, however, was asleep! They were hanging on for dear life to the sides of the boat and were ready to do whatever it took to save themselves. Some were probably bailing furiously. Yet, He was peacefully asleep, and they cried, “Lord, why do you sleep? Save us!”