When a concept starts to bite

This week I built the smallest project I could think of: a 30-day dumbbell habit, tracked by Claude. I type "done" after my workout, and it checks off the day and recalculates my streak. Day 1 took 5 minutes of lifting and considerably longer of building.

But the workout was not the point.

Somewhere in the middle, I almost made a classic mistake. I wanted a nice visual dashboard, so I nearly let it store its own copy of my progress. Two versions of the data sources, guaranteed to drift apart.

I knew the term for this. "Single source of truth." I could have defined it for you a month ago and tell you what it means. But I only understood it the moment my own little project tried to violate it. A view should behave like a mirror, showing whatever the data looks like right now. Not like an old photo of it.

That's the difference I keep running into. Reading a definition feels like understanding. Putting it to my Obsidian feels like I have learned it. It is not. A concept becomes yours when it starts to bite, when it pushes back against something you are actually building.

Until then, you have just memorized another noun.