From the Sheet Music at the University of Maine:


A SMILE WILL GO A LONG, LONG WAY
Words and music by Benny Davis and Harry Akst.
Published by Waterson, Berlin & Snyder Co., New York, 1923.

1. Smiling faces always find a welcome.
That’s why ev’ryone should learn to smile.
Remember after all,
Your troubles may be small.
Here’s a little thought that’s worth your while:

CHORUS: When you’re blue, and kinda lonely too,
You’ll find a smile will go a long, long way.
Though you’re down, don’t sit around and frown.
A little smile will go a long, long way.
Never grieve; just try and make believe.
The sky is blue altho’ you know it’s grey.
Don’t you pine; it’s just a waste of time.
You’ll find a smile will go a long, long way.

2. Once I used to think my case was hopeless,
Never wore a smile the livelong day,
But since I learned to smile,
My life has been worth while.
That is just the reason why I say: CHORUS

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You can hear a 1924 recording by Billy Burton at the Internet Archive.