The key is in what you said -- recognizing that it's impossible to know everything. This is true for me, you, and everyone else.
What this means is that it makes no sense to feel guilty or ashamed about it, since it's not only an inescapable situation, it's the same situation that literally everyone is in.
What should cause shame and embarrassment is acting like (or believing that) you know something when you don't!
I'm a big believer in two things related to this:
1) Kettering's Principle of Intelligent Ignorance. The most important thing to know is what the limit of your knowledge is. We are all ignorant of more things that we have knowledge about, after all, and knowing what you're ignorant of helps keep you out of traps and enhances your credibility.
In other words, intelligent people recognize their ignorance. Unintelligent people are blind to their ignorance.
2) Discovering that you're wrong about something is a moment to be celebrated, not ashamed of. Being corrected means that I've just become a little less stupid. That's a great thing! As a corollary, acknowledging to others that you've been wrong enhances your credibility to others. It does not reduce it.
Professionally, the important thing is that you have a overview-level knowledge of most things, and an in-depth knowledge of the things that are important to your position (and positions that you're aiming to achieve). That's a much lighter lift than trying to be competent in everything.