From experience, this is the formula we use when flying overnight to Europe: as soon as we board the plane, we set our watches for local time at our destination. When you see it is 2 am where you are going, that movie on your flight doesn't seem so appealing. You are better off trying to get as much sleep as you can on the plane. When we arrive, we DO NOT NAP!!!! Yes, we our brains are foggy, but if you plan for a "quick" nap, you will fall into a deep sleep, turn off your alarm and waste your first day. We plan at least one activity since there is so much to do and your time might be limited. A visit to one museum or some major tourist site will wake you up and you will be glad you did something productive on your first day. Even just walking around and people watching is so much fun in Europe! Plan for an early dinner and an early bedtime and you will be good to go for the next day. You will probably wake up early the next day, so it's ok to make morning plans. It's always a thrill to be in Europe - have a great time!