Why is it never easy?

I make a snap decision.  I'm going to charge some booze an my AMEX card, but the problem is, is that I'm pretty sure that it's maxed out.  Yes, that's possible, because it's a secured card; my credit has been in the crapper for a while and this is one way I decided to try to improve it.  So I promptly maxed the card out, mostly with drinks and extravagant tips.  For some reason, my credit is simply not improving.

I think, 'How can I justify walking back to the cab with $47 cash and carrying a bag of beer and wine, then bargaining the fare down?'  It simply doesn't make sense.  But I decide to give it a try anyway.  I grab one of those nifty "4 little bottles of wine equals one full bottle of wine" 4-packs and a few pounders of high alcohol malt liquor and head to the register, keeping my head down, sneaking peeks at the cab.  Still no interest from his end.  For that I am grateful.  Well, there is a line, and a problem with the credit card reader.  Shit.

Time is moving slowly here.  The guy in front of me obviously knows the cashier, and they are making small talk while the manager unplugs then re-plugs the credit card reader.  Time stands still now, as everyone just stares at the machine waiting for something, I don't know what.  I feel a little sweat pooling at the lower part of my back.  Soon, the guy in front of me pays, leaves, and I am exposed for the reprobate that I am.  I put the wine and beer on the counter, and say 'credit, please'.  Of course, I am told that the system is rebooting, and will be a minute.  At this point, I'm pretty sure the cabbie is wondering where I am.  But I dare not look. 

'That will be $11.79, please' she says.  I hand her the card, and she slides it through the reader.  I'm really sweating now.  'Hmmmm', it doesn't seem to want to take it.'  I say, 'OK, try it without the beer'.  She slowly pulls the 3 cans out of the bag; all eyes in the store are on me. '$8.99', she says.  She runs the card again, and I can tell she is a bit embarrassed as she looks at the reader.  'I'm sorry, sir, but it still won't take it.'  I'm panicking now.  I tell her, 'OK, I'll just pay cash for the wine'.  'You don't want the beer too?' she asks.  'NO' I practically scream as I throw a $20 at her.  She rings me up, I grab the change and my bag, head out through the rain, and jump into the back of the cab.  The cabbie looks at me, 'Everything OK?'  I say, 'sure, let's go.'  Shit.