Lyrics:

I know you know that we're through
I know you know what you got to do
Knowin' it, showin' it's just a part of it
But I got a clue
It ain't what I know that makes me blue
It's what I thought I knew

I lost a lot of things before you came
I know that losing, that's just part of the game
And I'm sure that I'll lose more
But all the same
It ain't what I lost that makes me sad
It's what I thought I had

Well, it is what it is, let it go
It ain't what it was, that's for sure
Things will be what they'll be in spite of me
Or you, even though
It ain't what it is that's such a sin
Its what it might have been

Oh, it is what it is, let it go
It ain't what it was, now we know
Things will be what they'll be in spite of me
Or you, even though
It ain't what it is that's such a sin
Its what it might have been