The way I've heard it is 'what most people think is overtraining is underrecovering'. My brother is a sports medicine doctor and what he told me is that actual overtraining is pretty much only seen in real athletes after months of sustained excessive training. What most people go through is actually called 'overreaching' and while it's not optimal you can keep going if you recover properly.
as they say: "you get stronger on rest days". this applies to both endurance and strength sports. the trick is to use your rest days productively; it doesn't necessarily require being inactive (for those who really want to go all in).
also, there's the principle of polarized training (for endurance sports): "go easy on the easy days, go hard on the hard days", because if you go to hard on the easy days, you can't go hard enough on the hard days.
a lot of people are under the impression that giving 100% every time, every day is the best way, probably thanks to years of training montages of sly dragging sleds through waist deep snow and karate-kid ... idk, kicking a tree really hard or whatever karate kid does, when actually it just leads to exhaustion and burnout.
Most of the professional athletes I've met get 10-12 hours of sleep. Now that I do lifting I need a solid 9 hours of sleep to recover and I need to stuff my face full of food to make gains.
Not impossible but certainly something that a lot of people can't do consistently if they want to have a job and do other things in life. Getting a half day of rest is almost a luxury for many.
yes, i usually slept without an alarm and there's a very noticable difference of about 2 hours between training and non-training days (i.e. 7 vs. 9 hours). i'm not a professional athlete, i'm a motivated amateur.
non-athletes often think it's nice to eat whatever you want and not gain weight, but it's actually quite unpleasant to having to force feed yourself all the time; not at least because you start wanting to eat certain meals - with a purpose. it took me a ridiculous amount of time and effort to put on some mass.
i used to go to the gym because i was bored. when i didn't feel great, i went to the gym because i knew i'd feel better afterwards. the gym was my safe space and my default activity. now that i have a family conditions have changed considerably; training is usually done late at night, in between obligations or on a few "me time" weekend hours for longer bike rides. works well enough, i can't complain.
