'The don't sleep too much and reduce to 7h' is such a horrible take. It really depends on the ppl. It's possible to do all the positive things (having great wlb, workout regularly, eat the healthiest food) and some ppl just need to sleep 8-9 hours. This is self help's guru level of advice
In my experience: Sleep as much as you can. Most probably don't have the luxury, but best is to not use alarm clocks. Your body knows exactly how much sleep it wants and needs, and your thinking brain has no business coming up with arbitrary hours of how long that should be.
> There is only one formula for healthy and refreshing sleep: Go to sleep only when you are very tired. Not earlier. Not later. Wake up naturally without an alarm clock.
[0] https://supermemo.guru/wiki/Formula_for_good_sleep:_free_run...