Maybe you're talking about the Silverstein/Kristofferson song, "Your Time's Comin"? This is the chorus:

You know she's a cheater, son
And you think that you're the one
That's got a lot of what it takes to change her;
I've no doubt that you can get her
You ain't much, but that don't matter
Nothin' suits her better than a stranger.
And the stranger man, the better
And the chances are she'll set her
Eyes on you, the next time she goes slummin'.
So just set back and wait your turn, boy
You got lots of time to learn, boy
Cool it while you can...
'Cause your time's comin'!