It's pretty common advice, but it hasn't made me a millionaire. However, it has driven me to create three projects: GamesDB, eft-graph, and most recently: Lysna.
"What should we play?" is a common question among my group of friends. We all have different preferences and deal-breakers, and I wanted to make service which would take all our tastes into account and suggest something to play. Before I could do that though, I needed data on all these games. GamesDB is a repository of structured data about video games, intended to fill that niche. Final note: turns out there's not a huge need for this 🤷
The second thing I worked on was eft-graph. I sunk about 100+ hours into the PC shooter "Escape From Tarkov" and eventually gave up trying to figure out the most efficient way to upgrade my hideout in the game purely from documentation. One thing I noticed, however, was that the various upgrades and their pre-requisites looked a lot like a network graph. Most of my time was just spent styling and doing data entry, but it resulted in a pretty cool way to look at that data.
The last thing I've been working on has been a way to easily control the extra monitor I had lying around in my apartment (connected to a Raspberry Pi). A few nights later, I had the beginnings of Lysna. It connects to Google Assistant (and other voice control services) through connector services like IFTTT to display anything I want. My s/o and I mostly use it to switch between chickens 🐔 and ducks 🦆.
(If you're here super early somehow, you'll notice Lysna isn't live yet. It will be, shortly.)