Bit of perspective
Not sure how or what happened enroute Hilo, but in answer to the second last post, how's this for a bit of perspective:
During the First World War, British and allied soldiers on sentry duty in the trenches were not to fall asleep. Those that did were executed by firing squad. Many were shot, yet, still, soldiers on sentry duty inexplicably fell asleep.
The body will sleep if severely fatigued, regardless of the perceived consequences.
It is therefore very important to power nap if you cannot stay awake in the cruise. Failure to do so is to invite micro-sleeps on final approach when falling asleep for even a second can be devastating.
Other than that, you may want to visit your doctor for specific advice on determining whether or not you suffer sleep apnea, and what to do about it if so.