Let's break it down.
The most important thing to consider for the sleep discussion is the established science showing some people are naturally "early birds," and others are "night owls."
Then as these things go, there is a spectrum with people falling somewhere on that spectrum—you might be in the middle and like to wake up at 10 am, for example.
So if science says that your biology is naturally included to wake up later and stay up later, what is going to happen to your productivity when you force yourself to wake up at 6 am because that's what some other successful person does?
Your productivity will go to shit.
You'll be tired, groggy, and not able to get into a flow state. You'll likely ruin your entire working day as you try to fix your body into someone else's box.
Reason two waking up early—if you're not a morning person—is BS is you should wake up after you are fully rested regardless of what time that is.
Ideally, you will wake each morning naturally without an alarm clock, which will be, for most people, after 7-8 hours of sleep.
This is why bedtime is more important than wake time. If you go to bed at 9 pm and you wake up at 5 am, and that works for you, great. Do it.
If you go to bed at midnight because that's when you find yourself getting sleepy, then you wake up around 8-9 am, great. Do that.
If you went to bed at 4 am because you worked late, wake up at noon. Do that.
See what I'm getting at?
Anything else is legitimately fucking stupid.
The flawed idea of the early bird gets the worm.
Forcing yourself to wake up to meet some target is nothing more than a societal creation.
Who says 6 am is the best time to wake up?
I've even seen people touting the benefits of waking up at 4 am.
Really? Come on.
If that works for you, then that works for you.
For me, if I forced myself to wake up at 4 am, I'd feel like shit every day. My productivity would suffer. My patience would be nonexistent. A zombie, I would not be fun to be around.
I'd roll out of bed, hating the process and setting my day up for grumpiness.
Then I'd drink more coffee than I should, causing its own set of problems.
Work would be a slog. It'd be forced.
If you are forcing yourself to wake up when you are not ready to, you will ruin your productivity, happiness, and cut years off your life.
Sleep is one of the most important considerations for long term health.
What makes this advice especially insidious is the fact that when you get enough sleep, everything in your life is better, and when you lack sleep, everything in life is worse.
So really, when you go to bed and when you wake are only considerations after the quality of your sleep is considered.
This is why I wake when my body tells me to. If I go to bed at 4 am, I tend to wake up between 11am and 12. If I go to bed at 1:45am like I did last night, I'm usually up around 10 am (like I did earlier).
Of course, I have flexibility since I set my own schedule. For most people, I don't recommend having a fluctuating schedule if you have commitments or work.
You're much better off going to bed and waking up at the same time each day.
Here are some strategies for creating a bedtime routine that will make falling asleep easy:
Then make this your routine every night.
After a while, you'll wake up naturally every day without an alarm while feeling rested and ready to get shit done. That's the best feeling. And that feeling is what you are trying to achieve regardless of what time you wake up each day.
So really all of this wake up early advice should be: Why You Should Be In Bed 8 hours Before You Wake Up Every Night No Matter What Or You Will Ruin Your Life.
You don't need to wake up early; you need to wake up when it's right for you and not a moment sooner.
Once you have your sleep routine down, if you want to wake up earlier, all you have to do is go to bed an hour early and start winding down for bed an hour early. The stronger your sleep hygiene is, the easier this will be, so make the investments.
Waking up early doesn't do anything itself. It can be good, bad, or just right, depending on your biology and how much quality sleep you are getting.
This thing this waking up early advice is missing is the goal of sleep: to wake up fully rested.
So when someone tells you to wake up early as a productivity tip, take it with a heavy dose of salt.
Then consider all the variables and how it may or may not work for you.