Mark: 
Smile, though your heart is aching, 
Smile, even though it's breaking 
When there are clouds in the sky, 
You'll get by 
If you smile 
Through your fear and sorrow 
Smile - and maybe tomorrow 
You'll see the sun come shining through 
For yooooooou 
Shane:
Light up your face with gladness, 
Hide every trace of sadness. 
Although a tear 
May be ever so near 
That's the time you must keep on trying, 
Smile - what's the use of crying
You'll find that life is still worthwhile 
If you just smile 

Instrumental

Mark&Shane:
That's the time you must keep on trying 
Smile - what's the use of crying
You'll find that life is still worthwhile 
If you just smile