The difference between checked and proved
A fast decision hardens into a fixed belief if you never go back to test whether it is still true.
Yesterday I found a hole in something I had already reviewed twice. Not a careless oversight - I had checked it. I just had not proved it. Those are different things, and the gap between them swallowed most of a morning.
Checking means looking at something and deciding it is probably fine. Proving means constructing a scenario where it would fail, and watching it not fail. One is an opinion. The other is evidence. I do a lot of checking and call it verification. Most founders do.
Beliefs that stopped being decisions
The deeper thing I noticed: I also corrected two other assessments yesterday, both things I had stated confidently weeks ago. Both turned out to be wrong in the same direction - I had assumed a problem existed and it did not. Clean corrections, fast. But it made me count how many other confident-sounding beliefs I am carrying that I have not tested since I formed them.
The dangerous kind is not the thing you know is uncertain. It is the thing that has settled into furniture. You stop seeing it as a decision. You stop asking whether it is still true. It just becomes part of how you understand the business.
Naval's line about deciding quickly with limited information is right. But it has a quiet partner: you have to know when your information has expired. A fast decision in September can harden into a fixed belief by October, and the fixed belief is the expensive one - because you have stopped questioning it.
Entrepreneurs are reasonably good at auditing numbers. Revenue, margins, burn. Those change in ways you can see. What we are less good at is auditing the mental model underneath the numbers: which customers actually matter, which products are working, which risks are still live and which dissolved months ago without anyone noticing.
The things I got wrong yesterday were not complex. They were just old. I had assessed them under different circumstances and never updated. The business moved. The assumption did not.
What I am trying to build is not the habit of deciding faster. It is the habit of dating my beliefs - knowing when I last actually tested something versus when I first formed an opinion and assumed it remained true.
Most of what you think you know about your own business is a decision you forgot you made.