I used to always wonder how someone could miss a flight until it happened to me a few months back. I thought I was leaving on an evening flight, but an early afternoon flight was booked, by myself of course. Since that happened I created a spreadsheet showing pertinent details for each flight that I update whenever I make a new booking, and make it a habit of keeping the sheet upto date. The sheet is very simple and I email it to my hotmail account whenever I edit it so that I have access to it from anywhere if I don't have my laptop with me.