I don't think it's good to regard it as "how dumb you were". I used to do something similar to this but this screwed me up a bit mentally, leading to a big lack of confidence.
How can I be confident or feel good about my decision if I am currently "dumb"?
You're not dumb if you make the best choices you can with the information you have at the time.
Sorry, I mean "dumb" in jest. The point is that introspection allows you to see what you knew based on what was available and what was short sighted and biased. I think that taking the time to consider decisions or positions at all is a huge step forward.
How can I be confident or feel good about my decision if I am currently "dumb"?
You're not dumb if you make the best choices you can with the information you have at the time.