Throughout this verse, David explains how he could not be afraid because he always knew that the Lord was with him. Because the Lord walked with him, David was able to traverse a dark valley fearlessly, perhaps even through death. The shepherds of ancient times carried a rod and a staff to protect their flocks. Like a shepherd protecting his flock from predators, David trusted the Lord to protect him with His staff and rod.
The Psalm, whose truth has been invaluable to so many people over the years, continues to be a powerful force for those who understand it and apply it to their lives. In the valley of the shadow of death, there is a pathway to life that leads to peace for all who follow the good Shepherd.
The valley of deep darkness and gloom has been filled with light and hope. This is because the Son of Righteousness has illuminated the path for all who have trusted in Him. As we follow the path that God has set for us throughout our lifetimes, let us put our trust in Him despite all disappointments and difficulties that may be encountered. “I will fear no evil: for thou art with me; thy rod and thy staff they comfort me.”

Dear Heavenly Father, thank You for being my good Shepherd and the Shepherd of all mankind. I place my complete trust in You. There is no circumstance beyond Your control and power. Please keep me close to You and be with me every step of the way. Please protect me from all dangers on my path and may I find Your provision, comfort, and peace to the very end of my life. 
In Jesus's name I pray. Amen.