Doing one thing really well.

That's the key to great products and services. Focus on doing one thing really well.

If you can't say clearly what that one thing is, you probably don't have one.

Great books do the same. Atomic Habits is about... habits. This is Strategy teaches... strategy. The Art of Possibility... well, you get the point.

It's tempting to do more, to make it a Swiss knife. But all it does is take away the edge.

"Who's it for?" and "What's it for?" demand that it's for someone specific and does something specific.