I day before and have a list on my phone for the things that can't be packed until the day of (cpap, meds, etc.). I mark them off as they get packed. Then I reset the list to use on the next trip.

My wife talks about packing early, but always ends up putting it off to the last night before the trip. Then she gets stressed out that she is missing something because she refuses to write down a list.

Outside of trips I can't keep track of most things because of ADHD and she is the reverse, not needing lists for most things. Our travel habits are the opposite of the rest of iur lives!