The threads our hands in blindness spin
No self-determined plan weaves in;
The shuttle of the unseen powers
Works out a pattern not as ours.

Ah! small the choice of him who sings
What sound shall leave the smitten strings;
Fate holds and guides the hand of art;
The singer's is the servant's part.

The wind-harp chooses not the tone
That through its trembling threads is blown;
The patient organ cannot guess
What hand its passive keys shall press.

Through wish, resolve, and act, our will
Is moved by undreamed forces still;
And no man measures in advance
His strength with untried circumstance.

As streams take hue from shade and sun,
As runs the life the song must run;
But, glad or sad, to His good end
God grant the varying notes may tend!

John Greenleaf Whittier

http://www.poemhunter.com/poem/overruled/