I have a little shadow that goes in and out with me,  
And what can be the use of him is more than I can see.  
He is very, very like me from the heels up to the head;  
And I see him jump before me, when I jump into my bed.  

The funniest thing about him is the way he likes to grow—
Not at all like proper children, which is always very slow;  
For he sometimes shoots up taller like an India-rubber ball,  
And he sometimes gets so little that there’s none of him at all.  

He hasn’t got a notion of how children ought to play,  
And can only make a fool of me in every sort of way.
He stays so close beside me, he’s a coward you can see;  
I’d think shame to stick to nursie as that shadow sticks to me!  

One morning, very early, before the sun was up,  
I rose and found the shining dew on every buttercup;  
But my lazy little shadow, like an arrant sleepy-head,
Had stayed at home behind me and was fast asleep in bed. 

Source: http://www.poets.org/viewmedia.php/prmMID/19964