Have you tried praying through the whole Psalter in a month? In our Missional Texts: Psalms and Genesis 1-11 class we spent some time discussing this ancient practice of the people of God, and are trying to practice it through the week as well.
As a catalyst for discussion we read a chapter from Ian Stackhouse’s The Day is Yours: Slow Spirituality in a Fast-Moving World (Paternoster, 2008), which was also reproduced, with permission, in the June 2010 issue of Encounters Mission Journal: Praying the Psalms
Here are some quotes I found particularly helpful:
The journey from Psalm 1 to Psalm 150 is the original odyssey: from the safety of a world where the righteous flourish and the wicked perish,  to a world where the wicked prosper and the righteous suffer,  and all the way through to a world where, whatever our experience of life, however unjust life has been, all ends in praise.  To pray the Psalms over a month is to embrace the whole gamut of human experience.
Waking up to whatever five psalms are before me is like waking up to greet old friends. I have been here before. I have heard these words already. Their familiarity is a comfort to my soul, and a relief from having to find the right words.
As Peterson continues: ‘Liturgy pulls us out of the tiresome business of looking after ourselves and into the exhilarating enterprise of seeing and participating in what God is doing.’
That we don’t identify with the particular mood of the psalm for that day, as is often the case, is not a problem according to this tradition of praying. Prayer is not in the first instance about my feelings anyway. I may identify with it, I may not. It doesn’t matter. The point of liturgy, as Heschel reportedly said to his congregation on one occasion, was not to express what they felt; rather it was to learn what the liturgy expressed.
In a strange and paradoxical way, this liturgical rhythm of prayer, far from supressing the emotions, in fact liberates them. As Kathleen Norris remarks… ‘To your surprise you find that the Psalms do not deny your feelings, but allow you to reflect on them, right in front of God and everyone.’
‘God behaves in the Psalms in ways that he is not allowed to behave in systematic theology.’  Our emotions are allowed to run wild. For those of us reared in the language of sentimental niceness on the one hand, and theological correctness on the other, the Psalms tutor us in a language that is far more daring. Without betraying the core ofIsrael’s faith, the Psalms say it straight.
It is no surprise to me, therefore, that people instinctively turn to the Psalms when they are suffering. How many times have I been aware as a pastor of how critical the Psalms have become for someone going through treatment for a cancer, another facing a bereavement, another off work with stress, still another waiting for an unfaithful spouse to return? Each one of them testifies to the relevance of these ancient words; for what the Psalms do is transfer us from the flatness, ishonesty and inadequacy of so much of our modern speech and into the ancient and extreme world of praise and lament, with all the ambiguity that living at the extreme implies.
When I pray the Psalms the whole company of saints is there with me: those who have gone before and those who are going now. Furthermore, even if I don’t feel what the Psalmist is going through, you can bet that someone else in the community of faith is. Even if I wake up joyful, for a change, and can’t hack why the Psalmist is so downcast – ‘why are so you downcast, I my soul?’  – the simple act of praying the Psalm reminds me that I am part of a community in which at any one time there are people grieving even as I am rejoicing. Conversely, while I am grieving, there are others who are rejoicing. Praying the Psalms tutors us in this community awareness.
Sometimes when I am praying a psalm a face will appear; someone for whom this Psalm describes actual experience. Other times the words of the Psalm sound for all the world like the latest news bulletin from Kosovo, or theCongo, and so, in a strange way, the ancient liturgy helps me to be more up-to-date than I would otherwise be. Precisely because the world hasn’t changed much, and human experience is awful a lot of the time, praying the Psalms, far from representing a retreat into private interiority, is an advance onto the concourse of life.
Reading Psalm 139 at the graveside of a person who died by suicide convinced me long ago that what the church needs in its public ministry, not to mention its public worship, is the gravitas of these ancient prayers: prayers where the words are weighty enough to hold us, cavernous enough for us to hide in.