have you got a brook in your little heart meaning:

Have you got a brook in you little heart, 
Where bashful flowers blow,
And blushing birds go down to drink,
And shadows tremble so?

And nobody, knows, so still it flows,
That any brook is there;
And yet your little Brought of life
Is daily drunken² there.

Then look out for the little brook in March,
When the rivers overflow,
And the snows come hurrying from the hills,
And the bridges often go.

And later, in August in may be,
When the meadows parching lie,
Beware, lest this little brook of life
Some burning noon go dry !