The Art of Divine Contentment: An Exposition of Philippians 4:11 by Thomas Watson. Excerpt 35

Watson continues discussing reasons to be contented, or "contentation," as he puts it.

3rd. excellency. Contentment makes a man in tune to serve God; it oils the wheels of the soul and makes it more agile and nimble; it composeth the heart, and makes it fit for prayer, meditation, &c. How can he that is in a passion of grief, or discontent, “attend upon the Lord without distraction?” Contentment doth prepare and tune the heart. First you prepare the viol, and wind up the strings, ere you play a fit of music: when a Christian’s heart is wound up to this heavenly frame of contentment, then it is fit for duty. A discontented Christian is like Saul, when the evil spirit came upon him: O what jarrings and discords doth he make in prayer! When an army is put into a disorder, then it is not fit for battle; when the thoughts are scattered and distracted about the cares of this life, a man is not fit for devotion. Discontent takes the heart wholly of from God, and fixeth it upon the present trouble, so that a man’s mind is not upon his prayer, but upon his cross. Discontent doth disjoint the soul; and it is impossible now that a Christian should go so steadily and cheerfully in God’s service. O how lame is his devotion! The discontented person gives God but a half-duty, and his religion is nothing but bodily exercise, it wants a soul to animate it. David would not offer that to God that cost him nothing.” (2 Sa. 24. 24) Where there is too much worldly care, there is too little spiritual cost in a duty. The discontented person doth his duties by halves; he is just like Ephraim, ” a cake not turned;” (Ho. 7. 8) he is a cake baked on one side; he gives God the outside but not the spiritual part; his heart is not in duty; he is baked on one side, but the other side dough; and what profit is there of such raw indigested services? He that gives God only the skin of worship, what can he expect more than the shell of comfort? Contentation brings the heart into frame, and then only do we give God the flower and spirits of a duty, when the soul is composed. Now a Christian’s heart is intent and serious. There are some duties which we cannot perform as we ought without contentment: as, 
(1.) to rejoice in God. How can he rejoice that is discontented? he is fitter for repining, than rejoicing.

(2.) To be thankful for mercy. Can a discontented person be thankful? he can be fretful, not thankful.

(3.) To justify God in his proceedings. How can he do this who is discontented with his condition? he will sooner censure God’s wisdom, than clear his justice. O then, how excellent is contentation, which doth prepare, and as it were, string the heart for duty? Indeed contentment doth not only make our duties light and agile, but acceptable. It is this that puts beauty and worth into them; for contentation settles the soul.
Now, as it is with milk, when it is always stirring, you can make nothing of it, but let it settle a while, and then it turns to cream: when the heart is overmuch stirred with disquiet and discontent, you can make nothing of those duties. How thin, how fleeting and jejune are they! but when the heart is once settled by holy contentment, now there is some worth in our duties, now they turn to cream.

Thomas Watson lived from 1620-1686, in England. He wrote several books which survive. This blog, God willing, will post excerpts from his The Art of Divine Contentment: An Exposition of Philippians 4:11, over a number of weeks, on Sundays.

My source for the text is here, and I thank the Christian Classics Ethereal Library for making this text (and many others) available. The previous excerpt is here.
  
Philippians 4:11 Not that I speak because of lack, for I have learned in whatever state I am, to be content in it. (World English Bible, public domain.)