Here is a message to encourage those who are in a dark valley. In it Psalm 23:4 is explained.
Psalm 23
The Lord is my shepherd; I shall not want.
2 He maketh me to lie down in green pastures: he leadeth me beside the still waters.
3 He restoreth my soul: he leadeth me in the paths of righteousness for his name’s sake.
4 Yea, though I walk through the valley of the shadow of death, I will fear no evil: for thou art with me; thy rod and thy staff they comfort me.
5 Thou preparest a table before me in the presence of mine enemies: thou anointest my head with oil; my cup runneth over.
6 Surely goodness and mercy shall follow me all the days of my life: and I will dwell in the house of the Lord for ever.