My seatmate on a Phoenix flight watched me repack at the gate and called it out
Window seat, 6am flight out of Sky Harbor, and TSA made me check my bag because of a full size bottle of sunscreen I forgot was in there from a lake trip in June. The lady next to me watched me dump everything into a trash bag at the gate and just said "you packed for the trip you wanted, not the one you got." She had one 20L backpack for a 9 day trip, same as me, and she wasn't even trying to rub it in. The part that got me was she said it in like 8 words and it stuck with me the whole flight. Now I keep a little ziplock of liquids in the top of my bag so I never dig for them again. What's the one thing you always double check before you walk out the door?