The song The Things That I Don't Know is performed by Marty Robbins .
I've heard it said, what you don't know
Won't make you blue
But somehow with these words I can't agree
'Cause it's not the things I know you do
That breaks my heart, you see
It's the things that I don't know that's killin' me
I don't see you when you meet him secretly
But I think your arms have held him tenderly
So it's not the things I know you do
That breaks my heart, you see
It's the things that I don't know that's killin' me
The little things that you don't notice
Hurts me so
Little things no one but me could ever know
I will keep them hidden so no one will ever see
It's the things that I don't know that's killin' me
I don't see you when you meet him secretly
But I think your arms have held him tenderly
So it's not the things I know you do
That breaks my heart, you see
It's the things that I don't know that's killin' me