Many wonderful things are in store for the one whose Shepherd is YHVH. The shepherd is the one who tends the sheep in all the meaning of tending. His staff is used to direct the sheep in the way they should go, so they get to green pasture and still waters. The shepherd knows where the green pasture and still water is.
Now if, as sheep, we say, No! I don’t want to go that way! then the shepherd uses his staff to grab hold of or correct us. It is not only a symbol of loving care, but correction. This is why His rod (of correction) and staff (of guidance) gives comfort.
Sometimes experiencing lack in an area is a way the Shepherd gets our attention, that He is correcting us, that we are not letting Him be the Shepherd by listening to His instruction! When we submit ourselves to the Good Shepherd, all the wonderful benefits of this psalm apply for us!
For further reading:
A Shepherd Looks at Psalm 23 by Philip Keller (excerpts)
Paths or Cycles of Righteousness – Hebrew word study (Brad Scott)