Business Insider's reporter regretted the timing of her long-haul flight to Japan.Monica Humphries/Business Insider In 2023, I embarked on one of the longest flights of my life: a 12-hour flight from Denver to Tokyo. My biggest mistake was booking a flight that didn't suit my sleep schedule. I was jet-lagged for days. I wish I picked a red-eye to help me acclimate to time in Japan. I hopped on a train heading to Denver's international airport with confidence.It was my second long-haul flight within a year, and I was convinced I had finally mastered the skill of traveling long distances.My travel pillow was packed, my AirPods were charged, and a bag full of snacks was stored safely in my backpack.I thought I had everything I needed.