This is dangerous advice, it really depends on what you're tired from and you can't apply it generally.
Eg tiredness caused by actual, diagnosed, Long Covid often does go away with more rest. In fact, even a tiny bit too much, too soon, can severely set back your recovery. To my understanding, parent's "just will yourself back into shape" advice is the exact opposite of what long covid patients should be told.
(Source: wife has long covid since January; her own experiences + what her therapists say from research and other clients)
To let you drag down by outer circumstances is more dangerous in my opinion. When you start running even if you would rather lay in bed that generates a lot of self-esteem. The resulting positive attitude may even be good for your immune system.
In some unfortunate situations you need to take some risks to get out of it.
It's not always about attitude, sometimes it's about physical healing. Sometimes, your body really just needs rest. Stop telling people stuff you don't know enough about.
Not overdoing it (to start with) is by far preferable tbh. My experience, for instance, is that inflamed achilles takes very long time (years) to go back to normal. To get it inflamed was fairly easy: resuming jogging a bit too swiftly after a winter break.
I know enough about people focusing too much on their wellbeing. You can trust me. Your mindset is more harmful than mine.
Sometimes the body needs rest, it's certainly true, but humans are adapted to a rather unforgiving environment in which you had to function even when in bad shape. Mind and body are connected.
Eg tiredness caused by actual, diagnosed, Long Covid often does go away with more rest. In fact, even a tiny bit too much, too soon, can severely set back your recovery. To my understanding, parent's "just will yourself back into shape" advice is the exact opposite of what long covid patients should be told.
(Source: wife has long covid since January; her own experiences + what her therapists say from research and other clients)