“Even though I walk through the valley of the shadow of death, I will fear no evil, for you are with me; your rod and your staff, they comfort me.”
David walks "through" the valley — he passes, he does not move in. The valley has an entrance and an exit.
A shadow can frighten, but it cannot wound — and a shadow only exists where a light is shining somewhere. The valley's dark is not the final word.
God does not promise a detour around the valley; He promises Himself within it. "You are with me" outweighs every why.
In the valley the psalm shifts: David stops talking about God and starts talking to Him. Pain shortens the distance of prayer.
The rod defends against danger; the staff corrects the course. Comfort comes from being kept by a present, attentive Shepherd.
Act: before breakfast, pray Psalm 23:4 aloud and put the name of your current valley in it: "even though I walk through…, I will fear no evil."