I usually have a “gather day” about a week before the trip. That gives me enough time to get anything I need from the store. The day before is when I do my active packing.
I do what Slyfox does, but I make a pretty thorough written list, and check it off before I head out. I also keep it with me for the return trip so I don’t leave items behind.
However, my husband always reminds me that most forgotten things can be purchased. I think that depends on the destination. In the USA, that’s pretty much true. Outside of the US, it takes a little more work.