He makes me lie down in green pastures;
he leads me beside still waters.
This is certainly a powerful image. Imagine for yourself a shepherd leading his flock onto a green hillside; once they arrive and the situation is safe, the shepherd lets the sheep graze and he watches them, enjoying the sight. The shepherd leads the sheep to those things which will help them flourish, those things for which they have a natural need. Green grass and water are the sustenance of sheep, and the shepherd brings them to these so that they can enjoy them. There is also a certain pleasure on the part of the shepherd to see that the sheep are doing well.
I think that the same may be said for God. He leads us to those things which will bring us to shalom, to wholeness, peace, health, to those things which will help us flourish. Perhaps too we may even speak of joy on the part of God, when he sees us enjoying life and the gift of existence he gives us.
Now there is another important aspect to bring to attention. The sheep don't begin their life and end it in green pastures the whole time; they don't spend every waking moment near still waters. There are moments of travel, when the flock has to be led from one spot to another. There may also be bears or wolves in the woods, and the shepherd has to protect them. The shepherd leads them to pastures and still waters, but this implies that they spend time away from these things.
So also in our case. The spiritual life is a journey, and there is no escaping this fact. There are stages which are more pleasant, which are more joyful, which seem a lot like spiritual green pastures and still waters. Other times there are inner battles, there is doubt, there are confusions and uncertainties. We have to go through these phases as well, if we are to advance at all. Sometimes there are bears; sometimes there are rocky cliffs; sometimes there are doubts and impulses in different directions. In everything the LORD leads us to him, to what will bring us to flourish, but this implies that we may spend some time away from this as well. We may spend some time in darkness and uncertainty.