I keep this little gem in the back of my moleskin. It is a Puritan prayer from the book "The Valley of Vision"
Man's Great End
"Lord of all being,
There is one thing that deserves my greatest care,
That calls forth my ardent desires.
That is that I may answer the great end for which I am made
To glorify Thee who hast given me being,
and do all I can for my fellow man;
verily life is not worth having
if it be not improved for this noble purpose.
Yet, Lord, how little is this the thought of mankind!
Most men seem to serve themselves,
without much or any regard for your glory,
or the good of others;
They earnestly desire and eagerly pursue
the riches, honors, pleasures of this life
as if they supposed that wealth, greatness, merriment could make their immortal souls happy;
But alas, what false delusive dreams are these!
And how miserable ere long will those be that sleep in them,
for all our happiness consists in loving Thee,
and being holy as Thou art holy.
O may I never fall into the tempers and vanities,
the sensuality and folly of the present world!
It is a place of inexpressible sorrow, a vast empty nothingness;
Time is a moment, a vapor,
and all its enjoyments are empty bubbles,
fleeting blasts of wind,
from which nothing satisfactory can be derived;
Give me grace to keep in covenant with Thee,
and to reject as delusion a great name here or hereafter,
together with all sinful pleasures or profits.
Help me to know continually
that there can be no true happiness,
no fulfilling of Thy purpose for me
apart from a life lived in and for the Son of Thy love."
May this encourage your heart as it encourages mine.