Our first trip, we got up around 4:30 AM to catch our plane. Got to our resort midday, had lunch in the food court, unpacked and headed straight to the parks. It was a bad, bad idea. My wife especially was so over being in the parks, she was tired and cranky. She still has memories of anger whenever she hears the soundtrack of Main Street Electrical, because she wanted to be out of there the whole time it was running through (although she actually does enjoy the parade itself)
Our second trip was a lot more relaxed. DW had just finished chemo, so we had to take it easy. First thing we did when we arrived in our room was nap. We woke up in much better shape after that.
Now we typically try to plan our first day as a non park day, even if it means a late evening arrival flight and basically just getting to the resort for sleep time. Of course, that's not always possible in the grand scheme of things, so really the main thing is to listen to your body. If you want to head straight to the parks first thing in the morning to get those first drops of magic, maybe look into heading back to the resort for a midday break. Or make that day an early night. If you know that you cannot function on 4-6 hours of sleep, make it a late morning park entry and try to close the park.
We started our Disney going with the 'No sleeping in Disney' mindset, but at the end of the day, you're not gonna enjoy yourself if you burn the candle from both ends. Missing out on a few experiences that would be enjoyable but are no must do to keep yourself as well rested as you can will result in a better vacation than doing it all and being exhausted.