I agree with Jim - I have always worked on the basis that I know I don't know everything, and in fact there's usually far more I don't know than I do know.

The key, I feel, is to accept this state of affairs and use the knowledge you do have to help find the right information when you need it. In terms of career progression, recognising that you will always need to support and collaborate with other people, either within your organisation or nowadays predominantly online via forums such as SQLServerCentral.com, is vital and is a strength not a weakness.

As has been mentioned, current and future software packages are so big and complex, no one person will ever be an expert in all areas. I usually go through all the menu options on a new package, noting new or changed items. At least I then have awareness of them.