Versatility and recovery. Versatility because I often pack for two climates in one carry-on. Recovery because everything gets stuffed, scrunched, and sat on, and I'm not ironing at 11 p.m. in a hotel room. If a piece comes out of the bag still looking like a piece, it earns its spot.

Not using the points and miles they've already earned. People hoard them for "the big trip" that never comes, and meanwhile pay full cash for flights they could have had in business for a fraction of the price.

Pick one big thing per day and let everything else be accidental. If today's big thing is the Vatican, the Vatican gets your full attention—go early, don't rush, sit somewhere afterwards, float about.
Three big things in a day means remembering none of them. One done properly beats three done in a blur.