I can't say I have ever felt "insecure" about not knowing everything, simply because I know and accept that it's impossible to know everything! I just take the view that if something comes up in my work that I've not encountered before then I find out about it, whether it be from someone else in my organisation or from the gurus in places like SQL Server Central and other sites like it.

The other thing is, just as you think you have mastered a technology (or whatever) a new version comes out with lots of new features making use of new technologies. You can never keep on top of it, all you can do is use past experience to get to know what is important to know in your job.

It's what has kept me in IT for 30 years, that non-stop learning process. Long may my ignorance continue!! 🙂