His point might have been that when you are tired your ability to do a great job is severely lessened compared to when you are not, this includes your ability to realistically evaluate how good of a job you are doing. Being tired means that you have impaired working memory, attention (especially vigilance), descision making abilities and general cognitive function.
I can't think of a more important predictor to the ability to get work done for long periods of time than knowing how to manage your life and time enough to not be tired all the time. They don't give a shit about how many hours you work, they care about how much necessary work you get done.
There's a trade-off to make here obviously, sometimes it's worth it. Some tasks can still be done if you are operating at 50% of your abilities, but if running a startup and parenting were that easy our world would be quite different.
I won't speculate on the specific situation you talk about because I don't know the details and you do. I'll give you the benefit of the doubt.
That said, your post rubbed me the wrong way because it's too much like the common geek macho bullshit that's too common in this community. You can't bully your brain into working better just with a self-help pep talk full of bland aphorisms and completely ignorant of modern knowledge about health and productivity. And you might want to avoid the comparisons to athletics - elite athletes talk about and track their rest obsessively. They don't show up to a tryout injured and defensively complain when it's pointed out.
And I should know better than to post any kind of general analogy as a way to illustrate a story here on HN with a bunch of smart people who'll punch holes in the technical impracticalities of such analogy... but yes, I took a negative word of "tired" and bent it to tell a story. Rest is important. Operating at 50% isn't good for the long haul.
I wasn't trying to suggest that being tired in a way that affects ongoing abilities to perform is a good thing. I just wanted to point out that if you just pop your head in to take a measurement of something, without the context of everything else going on, then that measurement might be off... ie, the investor seeing me as tired, without knowing it was because of the intensely productive and long week I had just come out of.
I was aware of my comment being close to one of those too typical "here's what's wrong with this post" comments, but you hit on two things that aggravate me the most in our community and I'm a bit of a pusher of the whole "work smarter, work less, get more done" line of thinking in general.
"the investor seeing me as tired, without knowing it was because of the intensely productive and long week I had just come out of"
That's why I gave you the benefit of the doubt, I figured this was part of your meaning and why you put the sports analogy in there. I'm with you 100% here, but when you drifted towards the glorification of long hours and threw in a "changing the world" (I hate this delusion with a passion, but you should obviously get a pass because with Hands.org you are one of the very few actually trying to do good) I got a bit snarky.
There might be a number of reasons why they do that. Maybe it's just a reason they give for rejection while the real reason is somewhat uncomfortable to say. Maybe they are afraid that you will burn out (and that's legitimate concern, take a break!). Maybe someone enthusiastic just gives a better feeling, vibe, something not very conscious. Because while you are with someone energetic, optimistic, you suddenly become like him. When you are with someone exhausted, you might start to feel the same.
I get your pain, I respect your hard work, but I'd suggest to put yourself in their shoes - maybe there's something you haven't noticed? :)
At the end of the day, and having talked to my team and family, I decided they just took a thin slice of experience and used it to make it into a negative... perhaps instead of being adult enough to say the real reason they didn't believe in me, the business, etc.