Psalms is a great book, which covers a variety of subjects. If I remember right, it is the most read book of the bible (?) or atleast devotionally. But then again I think "modern Christianity" mostly reads the bible only devotionally (as opposed to doctrinally or instructionally). Meaning many professing Christians don't really read the bible, but they will read Psalms as a "devotion". But David wrote most of the psalms and he was a "man of war". And many Christians don't realize they are in a war, and they lack the doctrine and instruction to fight in this war.
Many Christians (whether if they are truly saved or not) don't know their weapon very well (the bible, sword of the Spirit). It's like they are hiding in the trenches and and don't know how to reload their rifle, so they read the "instruction manual" as a devotion! And then only a few Christian soldiers are out on the front lines fighting in the war, and doing all the work. But just as soldiers receive badges, Christians receive crowns. I've heard a good sermon illustration about war and the Christian life. And its true, i can it see for myself as i compare it and as i continue in my walk, im gonna see some battle scars and brethren that have died in this war.
Still i myself need to stay challenged to stay in the fight as it gets discouraging. There will be rest soon, until then i shall keep my "feet shod with the preparation of the gospel of peace;" as people are still breathing and need to hear the gospel and be saved. Even the lost sinners play a part in this war and don't even know it... Their way of surviving is just pain selfish. No one can save themselves, and there's no life outside of Jesus Christ.
Ecclesiastes 8:8 There is no man that hath power over the spirit to retain the spirit; neither hath he power in the day of death: and there is no discharge in that war; neither shall wickedness deliver those that are given to it.