Concentration is not a talent. It's a very specific practice, fundamental to anything you want to accomplish. Concentration itself is a skill that grows with daily practice.
When I was a kid, I had difficulty staying on the same task. My daydreams were (and still are) incredibly vivid. I had a lot of physical energy, and I wanted to run around as a kid. And when I can't, being stuck inside studying, I'd have near lucid daydreams of running around outside. Combined with being able to pick up many things up, I become more and more intolerant of my own mistakes and challenging situations. As I entered my early adulthood, my experiences of life started narrowing down as I avoided challenges. And when I try taking on those challenges, I'd run straight into them.
It was later in life that I learned the methods for concentration practice. There are no shortcuts to concentration. There are no clever hacks. Searching for a shortcut is precisely why most people have difficulty concentrating. Your mind does not want to accept what you are doing here and now. So you think you have to "force" yourself to concentrate, and end up burning a lot of energy keeping you on track. This is NOT how you concentrate.
Concentration grows a little bit each time you practice, and the more you practice, the more you learn about how your mind works.
Growing the raw skill of concentration as you learn your primary art is itself the reason other skills take years of practice to master. It is also why, without practice, talent does not blossom into mastery.
"after just a few days, the four- and six-hour group reported that, yes, they were slightly sleepy. But they insisted they had adjusted to their new state. Even 14 days into the study, they said sleepiness was not affecting them. In fact, their performance had tanked. In other words, the sleep-deprived among us are lousy judges of our own sleep needs. We are not nearly as sharp as we think we are."
So, although you can get used to being sleepy, it's unlikely you're performance isn't being impacted. You could argue that the 2 week study wasn't long enough, but it still seems to show that you can't really judge your own cognitive performance, so any anecdotal evidence to the contrary wouldn't hold much water.
I play a text based online game where activity is extremely important and I often only have 3 or 4 hours of sleep every day, and even that is broken in to chunks so I can be online every 3 hours - and this is for the past 5 and a half years.
Outside of the obvious physical and mental stress it can put you under, you are perfectly right when you say that it takes time to perfect, at first I was tired from having 8 hours of sleep, now I can have 3 hours of sleep per night, wake up and operate at 100%.
I'm not sure when, but somewhere along the line I lost the need for sleep, I don't get tired any more or yawn and even on nights where I can sleep as long as I want, I find myself only wanting 4 or 5 hours anyway.
I'm without a doubt the highest ranked player on the game, fought for through perseverance and a refusal to let my ego take a hit, but was it worth it? I'm not sure.
Please note though you can train yourself to sleep only 4 hours a day, it doesn't mean you must. What I mean to say is, rest is essential to any long term productive endeavor. I think athletes and gym freaks can attest to this. How much you rest and how quickly recover from stress can decide how productive while you are awake. And probably affects your larger health situation on the longer run too.
>>but was it worth it? I'm not sure.
I won't comment on your habits and whats important to you. But speaking objectively. I would say its bad use of time.
If you are in need of entertainment, which demands a lot of engaging activity I would advice you start to learn playing a music instrument. Again not risking your health in the course of it, but music is a liberating experience. Especially if you learn how to play yourself. It can be very joyful.
And its generally a good skill to have and a lot better than fighting for internet points.
Few people in the US are shown how to study. People end up doing a wide range of things. But most of the methods that work seem to be something along the lines of: Clunking things so you use about 2/3 of your natural attention span 'studying' then review and repeat as needed. Get a good rhythm going and you can loose track of time. So, it's a good idea to take regular short breaks, just get back to it when your done.
You need to cover enough material that reviewing is not quite trivial, but no so much that your mind starts to wonder.