How can I keep from singing?

I was listening to the St. Olaf Choir singing two arrangements of this hymn. These lines especially stood out to me:

No storm can shake my inmost calm while to that Rock I'm clinging.
Since love commands both heaven and earth, how can I keep from singing?

The full text:

My life flows on in endless song:
     Above earth's lamentation,
I catch the sweet, tho' far-off hymn
     That hails a new creation.
Through all the tumult and the strife
     I hear the music ringing;
It finds an echo in my soul--
     How can I keep from singing?
What tho' my joys and comfort die?
     The Lord my Saviour liveth;
What tho' the darkness gather round?
     Songs in the night he giveth.
No storm can shake my inmost calm,
     While to that refuge clinging;
Since Christ is Lord of heaven and earth,
     How can I keep from singing?
I lift my eyes; the cloud grows thin;
     I see the blue above it;
And day by day this pathway smooths,
     Since first I learned to love it.
The peace of Christ makes fresh my heart,
     A fountain ever springing;
All things are mine since I am his--
     How can I keep from singing?