&gt; I found manual labour hard but overall easier hours by a big margin.<p>The toll adds up if you do manual labor long enough. Bodies are machines and they wear out.<p>&gt; I have physical issues from the non-physical work and I know people who&#x27;ve had (true) burn-out and stress-related illness.<p>Been there, done that. And these can be serious issues as well, but it&#x27;s not the same as dropping dead 2 days after you finally receive your pension because your body is done with living.<p>&gt; My personal experience is that I can keep going physically when I&#x27;m exhausted but productivity drops to near zero when mentally tired.<p>I think we all can relate to that. Which is why we - as a rule in the industry - estimate that people are productive in knowledge work for 4 to 6 hours per day.<p>&gt; My experience is that people massively underestimate the toll of non-physical work rather than that they underestimate physical work.<p>My experience is the opposite, people find it very easy to relate to things they have personal experience with and find it hard to relate to things that happen to others.<p>&gt; Sorry if your friends &amp; relatives are suffering from their jobs.<p>Where did my relatives come in?