Meaning: my memory is so bad… or I’m so forgetful…
Rewrite 1: I’d lose my tongue if it weren’t attached
Rewrite 2: I’d lose track of my keys if they weren’t in my hands
Rewrite 3: I’d leave my coat behind if I weren’t wearing it
Rewrite 4: I’d stop chewing if it didn’t mean food falling from my mouth
Comment 1: This cliché is really about bad memory, so I have skewed the rewrites toward that.
Comment 2: Before you jump all over me for using “weren’t” instead of “wasn’t”, consider that it is proper English to use “weren’t” in the subjunctive or hypothetical case.
More reading about clichés
What I found when I googled “clichés”:
• The Grand List of Console Role Playing Game Clichés: self-explanatory. If you’re into RPGs (role-playing games), you’ll know what this is about.