Realistically, Project 333 makes packing a snap - you don't have terribly much from which to choose, and if your garments were wisely chosen, most of them should go together pretty well. But I always find it comforting to have a plan in mind, when those phone calls arrive. I've had a few near misses recently with having to travel at the last minute, so I'm happy to have the following plan for the balance of the warm weather.
Travelling for me almost always involves flying - my relatives are scattered about the planet. Even on the hottest summer days, airplanes are cold (it's always WAAAY below zero at 35,000 feet), so a cardigan, a light wrap, and SENSIBLE shoes are always appropriate.
In these clothes, I could go straight to almost anything short of a reception with the Queen...
My packing gives me options from relatively dressy, in one of my dresses, with ballet flats and a scarf, to very casual - jeans and tee shirts. Because the weather is warmer and I'm wearing shoes without socks, I like having a few more shoe choices. Nothing much in the world packs flatter than ballet flats, so I don't feel like I'm crazy taking 2 pairs... A smaller handbag for everyday usage, a couple of scarves, and a few pieces of jewelry, and I'm ready to handle whatever is thrown at me.