For many of us, this psalm was our first Bible passage to put to memory. Jews and Christians often read it at funerals. Although it does carry hope of eternity beyond death's shadow, this passage is also about day to day life.
Sheep are dumb. Domesticated sheep without a shepherd have little chance of survival. They are preyed upon by a multitude of creatures from the tiny ked to the big cat. They don't readily migrate and will quickly overgraze their territory. Without men to dunk them in troughs laden with "flea dip", guard their pens from dusk to dawn, and get them moving along narrow passes to fresh grazing land, they would struggle to survive in the Fertile Crescent hills where still waters are hard to find.
David, who wrote this psalm, was the furthest thing from a sheep. A herdsman in his youth, he fended off lions and bears. He ruthlessly killed his enemies, beginning with Goliath, commanded 600 scouts against armies of thousands, and built walled cities and palaces. He was confident in his station as the rising king of Israel. This psalm is not about personal humility. It is about the elevation of a Great and Mighty Lord.
David implies, "If, to me, The Almighty is a shepherd, then what should He be to you?"
This is a declaration of dependence -- total dependence on the Almighty -- daily. As you read Psalm 23, think about how you can recognize God's providence in your daily life. If have good water, credit Him. If you've been given health, credit Him. If your sworn enemies have been kept at bay, credit Him. Commit yourself to be led by Him daily, even if the passes are narrow and your carnal instinct is to live only for what you know here and now. At the end of the day, aspire to His house, from here on to eternity.