I'm a sentimental sap that's allA love song that's not sentimental. Hart really wasn't a sentimental guy. So the first line is about how the protagonist is a "sentimental sap." There's self awarareness here. Making a kill, or a killing and taking advantage of someone are not good things.
What's the use of trying not to fall
I have no will
You've made your kill
Cause you took advantage of me.
I'm just like an apple on a boughHaving one's goose cooked is not a good thing either. It's an idiom that means you've had it, you're done for. Of course, there's a tradition of love poetry in which the lover is basically done for. Love is a destructive force that kills one's will. Hart was up on his courtly love tropes.
and you're going to shake me down somehow
so what's the use
you've cooked my goose
cause you took advantage of me.
I'm so hot and bothered that I don't knowHe gets a lot of mileage from idioms like "hot and bothered," which means sexually aroused. I'm putting all the idioms in bold face. Another courtly love, Petrarchan trope: both the presence and the absence of the beloved are troublesome. Back to the final A section of the song:
my elbow from my ear
I suffer something awful each time you go
and much worse when you go.
Here I am I with all my bridges burned.
Just a babe in arms where you're concerned
So lock the doors
and call me yours
cause you took advantage of me
Two more clichés / idioms. Burning bridges is cutting off connections with other people. A babe in arms is an innocent, defenseless person. You don't describe yourself that way, so once again, there is an ironic self-awareness here.
Prosodically, it's perfect, with the long couplet / short couplet / refrain structure.
The best love songs are not "you're wonderful," but "I fell for you even though you're not so wonderful, and I'm pretty much screwed." All the negativity here works wonders. All the cynical clichés.