It's not just because they're grumpy or nostalgic that old people complain when things decline. They're also the only first-hand witnesses — the only… - Paul Graham

Implementing something doesn't guarantee that you understand it, but it's among the best evidence that you do.

One of the most consistent mistakes I made when I was younger was to spend my time learning about things that other people thought were interesting — things that were cool or prestigious — instead of trusting my own curiosity.

You might find contradictory taboos. In one culture it might seem shocking to think x, while in another it was shocking not to. But I think usually the shock is on one side. In one culture x is ok, and in another it’s considered shocking. My hypothesis is that the side that’s shocked is most likely to be the mistaken one.