Actually - if you could only let it - your body would eventually find it’s own natural sleep rythm (depending on sunlight), which would be the perfect amount of sleep specifically and individually for you, and would also dynamically adjust itself with regard to weakening factors like fighting off an infection in it’s onset.
Nature is very good at those things - but getting there would need months of not interfering, and listening to your body’s signals (when it’s time to go to bed). If it was possible, that would be the most healthy thing to do.
But in a world full of alarm clocks, artificial lights, window blinds/shutters, and high caffeine (and other stimulant) intake - and where being on time is a highly regarded value - it’s entirely impossible to develop a natural rhythm, and as a result our body is completely off it’s mark and totally confused - so that we have to actively discipline ourselves to at least halfways healthy sleeping habits.
Over many years of repeated phases of both wanton sleep neglect and overdoing it, I’ve come to the conclusion that around 8 hours is the best dose for me - where I’m most creative, most mentally fit (quickest thinking, and least dumbness), and also most calm and serene.
My record low was 10 hours of sleep for a whole week. It was so bad that I would fall asleep while standing in a driving bus, and have that sudden wake-up convulsion at every turn it made. At the end I sometimes couldn’t read printed text, due to being unable to focus my eyes. I was so wound up that despite my sleep deprivation I couldn’t really sleep in bed without calming myself down with a beer first. I also was unable to think straight, had to stop walking and stabilize my view to see where I’m going, I had shaking hands and tunnel vision. I failed at the simplest every-day tasks. It was really, really bad.
On the other extreme, I had times where I’d sleep 12h+ each day - to the point where I was tired and lethargic all day, because of too much sleep. But you can’t pull that through for long, because you’ll start to simply wake up, being unable to sleep again 
(unless you have sex that moment, which I found to be very effective at letting me sleep a short while again)
If you don’t get enough sleep, you are more irritated and short-tempered, and also more hungry (if your body feels strained it wants more calories by default) - and your brain doesn’t work as well/fast.
So… getting a healthy dose of sleep is really good for you
