Hi Imorovan
I think the 23 Psalm was one of the first Psalms I memorized and repeat to myself often.
My thinking has been that the valley is the life I am walking in now and the "shadow of death" is the possibility of the second death. A shadow can only be created in the absence of light and the light we need to overcome the shadow is our Lord and Saviour, Jesus. The rod and staff are weapons of defense that David would have been familiar and trusting in and he assigns them to our Lord as weapons to protect us from Satan's power, the second death.
We need not fear Satan's power as our Lord Jesus is the light we need to follow to destroy the power of the shadow while we walk through the valley, " i shall fear no evil, for thou art with me".
Very interesting post, thanks.