When I learned how to tie my shoes as a kid, I was taught what I now know is a granny knot. The problem with this knot is that, at least for me, it came undone easily, causing me to have to re-tie it several times a day. Eventually I started double-tying my shoes, making tying and untying them a total pain, and a little goofy-looking. Why didn't other people's shoes come untied? What secret did they know? Was I walking wrong?? Well, it took three decades, but Adam Lisagor of the men's style show Put This On blew my mind by explaining the reef knot -- a stronger, flat-lying knot that stays tied. It's very similar to the granny knot, you just change the direction of one loop and your life will change. Thank you, internet.
Here's a TED Talk -- yes, really, an actual TED Talk (albeit just three minutes long) showing exactly how this works. Enjoy:
See also: Put This On episode 2, embedded below. It's a ten-minute show about shoes, including a brief segment explaining the reef knot at the 8:15 mark.