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, and I nearly let it store its own copy of my progress. That would have meant two copies of the same data, slowly drifting apart.

I knew the term for this: "Single source of truth".

The data should live in one place, and one place only. The dashboard just displays it, reading fresh from the source every time. It never keeps a copy of its own. I could have defined it for you and told you what it means years ago. But I only understood it the moment my own little project tried to violate it.

That is the difference I keep running into. Reading a definition feels like understanding. Putting it into my Obsidian feels like I have learned it.

But 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.