In short, the Psalms provide the language, the aspirations, the energy for the community as it comes together in prayer, and they then call into being and are formative for the activities of prophets, wise men, and historians. The Psalms initiate; the prophets follow. The inner action of prayer takes precedence over the outer action of proclamation.
The implication of this for pastoral work is plain: it begins in prayer. Anything creative, anything powerful, anything biblical, insofar as we are participants in it, originates in prayer. Pastors who imitate the preaching and moral action of the prophets without also imitating the prophets' deep praying and worship so evident in the Psalms are an embarrassment to the faith and an encumbrance to the church.
Working the Angles: the shape of pastoral integrity, by Eugene Peterson, page 40