First of al is @Pops going with you?I will be experiencing that with a trip to Amsterdam in less than four weeks. My plane departs Austin at 6PM and arrives in Amsterdam at 10:15AM the next day. That's a direct flight.
I'm the type that can doze off for a minute, wake back up, doze off, back awake, and so on. I somewhat purposely do this. Mostly because I have no clue what I'm like when I'm asleep -- lol, that's what living alone for many years will do. Unfortunately, you can get by with that on a domestic flight. But across the pond is another story.
Second, the day before you leave - sleep as long as you can (go to bed early, sleep in) - plan on a light day the day you land in Amsterdam ... power through the day and try to get to sleep early-ish that evening. If you nap during the day I have found it hard to get yourself back onto a good sleeping rhythm. Your body simply doesn't know what time it is!
Good luck and have fun in Amsterdam!