a happy heart makes a stone a flower.

The Butterfly, Johann Georg Meyer Von Bremen

The Example  
W.H. Davies

Here's an example from
          A Butterfly;
That on a rough, hard rock
          Happy can lie;
Friendless and all alone
On this unsweetened stone. 

Now let my bed be hard
          No care take I;
I'll make my joy like this
         Small Butterfly;
Whose happy heart has power
To make a stone a flower.