I hope I am not creating more anxiety with all my bloviation on this subject.

It could be as simple as this -- when shooting in natural light conditions, set your ISO to 400 and go about your business. When operating outside drop it down to 100-200. It's not something that needs to be pondered a great deal or maneuvered back and forth.

I just want people to understand how the number can hurt you or help you in low light conditions.

I save my anxiety for the big stuff!

Jean