When I was still flying for United, I would have the first flight out at 5:50 a.m., which meant that I would be awake at 3:30 a.m. After a 6-hour flight and arriving on the west coast, I would have a 2 or 3 hour rest followed by a short flight to Denver, San Diego, etc. and then a stay over and then repeat the next day, only in reverse. Do that for two days, take a day off and then repeat for the next two days and have weekends off "most" of the time. My sleep habit was all over the place, but never had any issues with being able to fall asleep. I think some people, like me, are like cats. We can lay down and doze anywhere anytime off with no problems. I also believe that it's called fatigue. Problem was that I had insomnia after I retired. I would not do drugs or alcohol, but I would read or play on my tablet until sleep would finally come.
If a flight would become available to Hawaii on the weekend, I would give up my weekend to fly there occasionally.