Here's TW, in "The Art of Divine Contentment":
"[This doctrine] shows how a Christian may come to lead a comfortable life, even a heaven upon earth, be the times what they will: by Christian contentment. The comfort of life does not stand in having much; it is Christ's maxim, 'man's life consists not in the abundance of the things which he possesses,' (Lk. 12:15)--but it is in being contented. Is not the bee as well contented with feeding on the dew, or sucking from a flower, as the ox that grazes on the mountains? Contentment lies within a man, in the heart; and the way to be comfortable, is not by having our barns filled, but our minds quiet. The contented man, said Seneca, is the happy man.
"Discontent is a fretting humour, which dries the brains, wastes the spirits, corrodes and eats out the comfort of life. A drop or two of vinegar will sour a whole glass of wine. Let a man have the affluence and confluence of worldly comforts, a drop or two of discontent will embitter and poison all."
