Being your slave what should I do but tend
upon the hours, and times of your desire?
I have no precious time at all to spend;
Nor services to do, till you require.
Nor dare I chide the world-without-end hour
Whilst I, my sovereign, watch the clock for you,
Nor think the bitterness of absence sour
When you have bid your servant once adieu;
Nor dare I question with my jealous thought
Where you may be, or your affairs suppose
But, like a sad slave, stay and think of nought
Save, where you are how happy you make those.
So true a fool is love that in your will,
Though you do any thing, he thinks no ill.
– William Shakespeare, Sonnet 57
http://www.shakespeare-online.com/sonnets/57detail.html