Because...

William Shakespeare. 1564–1616
 
Sonnet 57
 
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.