Packing is not my Favorite of Pasttimes

I'm leaving tomorrow for my trip across the US (or up the US I guess) to NC, NYC, Albany NY, Cincinnati, South Bend, and then Cincinnati again. From there, I'll fly to Venice on September 7. I've been trying to pack, and have failed miserably at being frugal. So far I have sent two suitcases with Marco that I will check on the way to Italy and am now packing a carry on to bring with me to NC and NY. The problem is that I have too good of an imagination and can easily make up all of the scenarios in which I will definitely need every piece of clothing and pair of shoes that I own. And THEN I get fed up with myself and leave the one thing that I actually did need. I am also drawing on the experiences that I had when I studied abroad in Rome, especially the time I realized that I forgot my toenail clippers - I searched high and low for them in the grocery store/super-markets, in the pharmacies, and in countless other places that wouldn't make sense for 2 months. Finally I found them in the hardware store on the other side of the city, right next to the hammers and saws. I love Italy, but I trust what I know in America - and I want to be prepared this time....apparently with three huge suitcases.