This song was featured in a 1931 Merrie Melodies cartoon which you can see on YouTube.

Lyrics from the sheet music at Baylor University:


SMILE, DARN YA, SMILE
Words by Charles O’Flynn & Jack Meskill; music by Max Rich.
Published by De Silva, Brown, and Henderson, Inc., 1931.

1. Let’s all get together with this one thought in mind:
Make this world a better, brighter place.
Tell each “Blue Nose” and “Joy Killer” you ever find:
“Hey there! Wipe that frown right off your face!”

CHORUS 1: Smile, darn ya, smile!
You know this old world is a great world after all.
Smile, darn ya, smile!
And right away watch “Lady Luck” pay you a call.
Things are never black as they are painted.
Time for you and joy to get acquainted.
Make life worth while.
Come on and smile, darn ya, smile!

2. What’s the use of walking in the shadows each day?
There’s no sense in looking for the rain.
Here’s the surest way to drive the shadows away:
Follow this advice; it’s mighty plain:

CHORUS 2: Smile, darn ya, smile!
For there is nothing that you cannot overcome.
Smile, darn ya, smile!
And where the clouds appear, you soon will find the sun.
Life is really only what you make it.
Stand right up and show them you can take it.
Make life worth while.
Come on and smile, darn ya, smile!

- - -
There are several recordings available but most have only the chorus sung. But I was able to find this one on the Internet Archive:
Ambrose and His Orchestra, on Electrola EG 2474, 1931.
and this one on Spotify:
Billy Cotton and His Band
that include the first verse.