Honestly, I do not know how you guys do this.
I think I pack the night before - that's what I always do - for several reasons.

Sometimes I need the clothes I'm packing right up until the day before - some favorite stuff I want to wear both here and there, like my comfy sandals. I also don't want clothes to get wrinkled sitting in a suitcase any longer than necessary. If I pack days ahead, I forget what I packed and have to take it all out and double check then repack. So, for me it's easier to have a list and a plan but not execute it until the night before.

I do put aside things as I come across them that I know I will bring. Like I bought travel-size sunblock and bug spray last week, and it will go in the clear quart bag with my "3-oz or less" liquids (I don't check luggage either, I only carry on). I bought a couple of books about/by Jamaican authors and set those aside awhile back. A few days ago I did the winter-summer clothing switch in my dresser and closet and made sure the clothes I like to wear in JA came up with the summer stuff. I have already gotten small US bills, my passport, printed my boarding pass, etc., and that is all by my backpack. This time I time I will be flying with a terrible cold, so I bought cold medicine and those ear plugs that help protect your ears from pressure change - EarPlanes, they're called. They're by the backpack too.

I did forget one thing I'll have to run by the store for later, and that load of laundry is in the dryer. But I'll be packed before bed, with everything crossed off my list. And as has been said...if i have my passport and money I'm going to be able to handle anything that comes up

Happy trails everyone!