I Thought I Heard You Knocking

I thought I heard you knocking As I sprung up from my chair Flung the door wide open There was no one standing there It's getting harder every moment To tell what's really real Sometimes it ain't the things you know It's more the way you feel I thought I heard you knocking Tapping soft and light Like the sounds an old house offers When it settles for the night You used to be just as familiar Like whiskey on my breath Now whenever you come calling You scare me half to death