Not the person you responded to, but he/she may be referring to there being other factors (unrelated to sleep) that may most likely be contributing to one's happiness factor, such as pre-existing health conditions (e.g., depression), relationships (both romantic and non), etc. A person who's just starting a new relationship and is still in the "honeymoon phase" might rate their happiness higher despite a lack of sleep.

The methodology the parent links explicitly tracks multiple positive and negative factors and isn't explicitly tied to sleep.

Personally, sleep is a huge factor in my happiness, so tracking it is pretty important.

Being mindful of your own emotional state presumes that you understand it. And judging by years and years of psychology, we're pretty bad at understanding ourselves.

Not really. If they take the time to observe their feelings, most people know they are happy, anxious, stressed, angry, irritable, manic. They don't know WHY.

Being mindful of your emotional state allows you to try to dig into why you are currently feeling that way and what is the source of the emotion. That's what we are pretty bad at understanding :-)

As a counterpoint to this, I'm absolutely terrible at even knowing when I'm anxious, stressed, angry, etc.

For me I end up externalizing my emotions by saying "I'm not in a bad mood, it's just this (annoyance/distraction/external factor) that's making things hard for me!" and failing to realize that it could be something that would normally not faze me, and it's really me that's blowing things out of proportion.

This is something I used to be much better at back when I used to practice mindfulness meditation. Being able to stop in the middle of a situation and recognize that you may not be in the best state of mind is an important skill that I have totally lost over the past few years.

Yeah, practice really helps. I’m mindfulness meditating again for exactly this reason, to get back on top of mood.

But externalizing is miss understanding the WHY as much as not understanding the root emotion.

Lifestyles, philosophies, religions can optimize for happiness or truth ... pick one. The HT theorem.

Or you could optimize for happiness-truth product. This would lead you to lifestyles, philosophies, and religions which remove any negative correlation between happiness and truth (which I would argue have no inherent, unavoidable relationship with each other).

Matt Ridley, the author of the Rational Optimist, disagrees.