It wasn't until I inverted the passage that it became clearer to me.
The Lord is not my shepherd, I shall be in want. (This means if I constantly want something, then the Lord may not be my shepherd.)
He doesn’t make me lie down in green pastures,
He doesn’t lead me beside still waters,
He doesn’t restore my soul.
There's a newish song on the radio by Unspoken called "Who you are." It's one of my favorites because aside from the catchy melody, the lyrics really make you think. The gist of it is that you can change who you are no matter how far out there you've gotten.
Of course, this is the type of message that has been sung by followers of God since Abram got a syllable added to his name. So, why does it matter?