Some motivational sites claim that if you want to be successful, you sleep much less than the average person. The argument is that if you sleep less you have more time to get work done and be productive.
I have a few problems with this type of advice. I have no doubt people who can pull this off exists. But you have to adjust that to yourself individually, to the tasks you perform and to your schedule.
I have a dayjob and are ~9 hours per week in the office (including commute). I still can squeeze in a few hours of gamedev into my schedule depending how draining the task at work were. In my experience, sleep deprivation is extremely bad for my productivity and will eliminate these few hours of gamedev in the evening. Instead, I spent these hours taking a nap because I am exhausted, later unable to go to bed at a reasonable time.
From the start of this month my productivity hit a low because I have screwed with my sleeping schedule, sleeping an average of 5 to 4 hours per day (6 including naps) this and last week. You can probably tell by the fact I haven't written many blogs this month so far. In order to be productive (whether it is coding or writing blogs), my brain needs to be in good shape in order to perform them.
That means: enough sleep, enough sun exposure ("recharging" my nerves), a bit of workout (taking a walk and doing sit-ups in my case), healthy diet (lotsa bluebewwies!) and being in peace of mind (I can't code when I am emotional distress). If one or more of these things are lacking, I am simply not in the shape for these kind of tasks. When tired, I am much better at doing art or music, which flows much better then.
Contrary to the initial advice (sleep less, get more work done) sleeping less actually impacts my ("logical") productivity negatively. However, your aim should create the conditions and environment required that enables you to be productive. If getting enough sleep is one of them, you shouldn't ignore that.
(There may be other reasons why sleep is a requirement for me to be productive, namely that my energy in general is low; it can be raised by correct posture or working out more. Still working on myself :])
It's always good to foster good habits to grow. See the basic point in advice given and see what you can adapt, keeping
in mind your own strengths, weaknesses, daily routine and habits.
Just keep in mind not every advice is useful to you or directly applicable to your life. You are on a unique journey and your journey is never the same as someone else's.