Here's an excerpt from Dr. Powlson:
From Jesus' point of view, there are two fundamentally different ways of doing life. One way, you're connected to a God who's involved in your life. Psalm 23 is all about this: "The Lord is my shepherd ... and his goodness and mercy surely follow me all the days of my life." The other way, you're pretty much on your own and disconnected. Let's call this the antipsalm 23: "I'm on my own ... and disappointment follows me all the days of my life."
I've struggled with depression, low self-esteem, anxiety, excessive need for approval, selfishness and pride and can certainly recognize that many of the lowest points of my life were times where the antipsalm 23 more accurately described my mindset than Psalm 23.