I have a travel checklist. Every time I'm packing for a trip, I print the checklist and check everything off the list (I've learned the hard way that it's a very useful thing for me).
I'm going on a trip and was going around the house checking off the final things on the list. I had packed all the clothes last night and was now checking off things like "pack phone batteries", "pack computer and power cord", when I noticed my luggage sitting in a corner, and I realized that I didn't have a "take luggage" reminder, and I could see myself leaving the luggage (not missing one item inside it). So I added one other item to my checklist: - take luggage!