Here is a wealth of insight on a great selection of Psalms which will help preachers and all believers to appreciate their richness and depth of meaning. For example, the author comments on Psalm 23:

David wrote this Psalm at the height of his maturity when he could have said as most men in this world say, I can manage my own life. I don’t need anyone else, I’ll sort out my own problems, but he didn’t. Even though he reached the top of his career if you like; even though he was the top man of his nation, the King of Israel, he was saying: I am a sheep and I need a shepherd. This Psalm is not for those who are dying, it is for those who are living. One reason why we apply it to death is that in the Authorized Version the word death was put into the Psalm and it is not there. It is, Yea, though I walk through valley of deep darkness I will fear no evil. You can walk through that valley tomorrow morning without dying. It is also due to the inclusion of the words at the end of the Psalm forever , making it a reference to the future life. But in fact, if you have a Bible with marginal references, you will notice at the bottom it is Hebrew as long as I live . Now Christians can read eternity into that, but David was talking about as long as he lived here. So this Psalm is to help you Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, next week - however near your death or far from it you are.