The best book ever written on the subject of contentment is "The Rare Jewel of Christian Contentment" by Jeremiah Burroughs. Here are a few samples for your enjoyment:

The way of contentment to a carnal heart is only the removing of the affliction. O that it may be gone! 'No', says a gracious heart, 'God has taught me a way to be content though the affliction itself still continues.' There is a power of grace to turn this affliction into good; it takes away the sting and poison of it.

Of his fullness do we receive grace for grace; there is strength in Christ not only to sanctify and save us, but strength to support us under all our burdens and afflictions, and Christ expects that when we are under any burden, we should act our faith upon him to draw virtue and strength from him.

There is no condition that a godly man or woman can be in, but there is some promise or other in the scripture to help him in that condition. And that is the way of his contentment, to go to the promises, and get from the promise, that which may supply.

A heart that is full of grace and goodness within will bear a great many strokes, and it will never make any noise, but if an empty heart is struck it will make a noise.