Sparking joy is part of it. Apartment Therapy recently asked Marie Kondo how to pack a suitcase, and while it's not the most mind-blowing video we've ever seen, it did spark joy in revisiting packing best practices.
For those familiar with the KonMari method™, the packing video won't come as a surprise, keeping in line with the Japanese consultant's basic tenets. For the rest of us, there are organizational principles to ponder.
One interesting thing the video unveils is that Kondo likes to stack folded clothes vertically instead of packing clothes flat, the most common method. The vertical method makes sense on a couple of levels: it is more space-efficient, and allows the traveler see everything in one fell swoop.
(She doesn't roll clothes exclusively, but seems to do a mixture of both depending on the item. In terms of folding, she defaults to the KonMari method.)
Kondo also likes to keep items that need to retain its shape near the top of the suitcase handle, which intuitively makes sense.
Though there is debate as to whether rolling clothes or the KonMari folding method is better for traveling, Reddit user datamer has this to say:
KonMari folded clothes fit perfectly into my packing cubes, much better than rolled clothes. Depending on what I'm packing, I'll unfold them once and have them fill out the footprint of the packing cube, or I'll keep them folded all the way and put two little stacks in there.
I'd much rather pack uniform rectangles than cylinders of different diameters, and I find there's much less wasted space in the 'negative' areas around rectangles vs. cylinders.
Other than that, the packing lessons seem pretty basic: curate what sparks joy, fold socks into bras, organize like with like, use pouches (or packing cubes), etcetera.