I used to have this anxiety sometimes too but there's a few things that help me deal with it:
* Remember that other people have these same feelings. You're not alone and it's normal.
* Anyone who would think badly of you just for not knowing one simple thing is an asshole and was just looking for an excuse to be a dick. The problem is with them, not you.
* Nobody can know everything. Even the person you most admire and respect professionally has areas where you know more than them.
* Work hard, strive to improve your knowledge and skill set. This is all anyone can do.
* Remember that other people have these same feelings. You're not alone and it's normal.
* Anyone who would think badly of you just for not knowing one simple thing is an asshole and was just looking for an excuse to be a dick. The problem is with them, not you.
* Nobody can know everything. Even the person you most admire and respect professionally has areas where you know more than them.
* Work hard, strive to improve your knowledge and skill set. This is all anyone can do.