I cannot sleep—my nights glide on

In one unbroken thought of thee;

And when the gloomy shades are gone,

I start the dawning light to see.

And as I watch the rising morn

Gain slowly o'er the yielding sky,

And mark another day new born,

That glows so brightly—yet must die—

I think how all the hopes we cherish

As transient, though as bright, will be;

And frailest of the hopes that perish

Were mine, that told of love and thee!

Louisa Stuart Costello

http://www.poemhunter.com/poem/lines-i-cannot-sleep/