Enjoy the present, whatsoever it be, and be not solicitous for the future; for if you take your foot from the present standing, and thrust it forward towards tomorrow's event, you are in a restless condition: it is like refusing to quench your present thirst by fearing you shall want drink the next day. It it be well today, it is madness to make the present miserable by fearing it may be ill tomorrow -- when your belly is full of today's dinner, to fear you shall want the next day's supper; for it may be you shall not, and then to what purpose was this day's affliction? But if tomorrow you shall want, your sorrow will come time enough, though you do not hasten it: let your trouble tarry till its own day comes. But if it chance to be ill today, do not increase it by the care of tomorrow. Enjoy the blessings of this day, if God sends them, and the evils of it bear patiently and sweetly, for this day is only ours: we are not yet born to the morrow. He, therefore, that enjoys the present if it be good, enjoys as much as is possible, and if only that day's trouble leans upon him, it is singular and finite. "Sufficient to the day (said Christ) is the evil thereof": sufficient, but not intolerable. But if we look abroad, and bring into one day's thoughts the evil of many, certain and uncertain, what will be, and what will never be, our load will be as intolerable as it is unreasonable.
~Jeremy Taylor, The Rule and Exercises of Holy Living, 1650 (London: Rivington, 1870), chap. II, p. 106.
"My experience," said an old gentleman to me, "has been that I never could succeed in getting the special kind of happiness I had wanted or hoped for, but that other kinds of happiness which I did not want or had never hoped for were supplied to me, in the course of life, most lavishly and abundantly. I therefore ended by discovering, though it took me a long time to make the discovery, that the right way to enjoy the happiness within my reach was not to form an ideal of my own and be disappointed when it was not realized -- for that it never was -- but to accept the opportunities for enjoying life which were offered by life itself from year to year and from day to day. Since I took things in this temper, I have enjoyed really a great amount of happiness, though it has been of a kind entirely different from anything I ever anticipated or laid plans for when I was young."
~Philip Gilbert Hamerton, The Quest of Happiness (Boston: Roberts Brothers, 1897), pp. 175-176.
Both excepts taken from The Art of Contentment, edited by Edgar Andrew Collard (1974)