The responsorial psalm for the Fourth Sunday of Lent gives us a vision of a radically God-centered life. And, in this case, radical does not meet revolutionary or abrasive or extreme. No, the word radical comes from the Latin word radix, which means "root." To center our lives on the God who is our shepherd is to go back to the very root of life, to the one who gives us everything we need.
And we can be grateful that God repeats this pattern throughout all of creation. Green pastures are naturally going to be balanced by dark valleys, but, in both joy and sorrow, the Lord provides for us and walks beside us.