I feel stupid compared to my peers

All the time. There's actually a name for that, you know: academic impostor syndrome. When I started my Master's degree, we actually got a talk from one of the professors about impostor syndrome; it's apparently quite common in grad students, so they wanted to make sure we were aware of it so that we wouldn't doubt ourselves too much and just give up on our research.

Despite that it's common in grad students, students of any education level can and will experience it. The thought that everyone else is smarter than you is totally normal, and the best way to handle it is simply to remind yourself of the positive things (like the fact that you get mostly As).

I know how you feel, though. I constantly feel less sharp, less articulate, less insightful than people in my PhD program. People are constantly using words that I don't know or understand when discussing even just the readings we've done, and I sit there feeling like a complete idiot, like I don't belong in that classroom...but I remind myself of my hard work, the fact that I got nothing below an A during my Master's degree (including on my thesis), so I did get there on my own, I do belong there.

Is feeling stupid normal?

Feeling stupid can obviously have a negative impact on mental health. It can be a sign of social anxiety disorder where the thought of looking stupid or saying the wrong thing in front of other people holds you back in life.

How do I stop feeling stupid?

How to Deal with Feeling Stupid and Improve Your Self-Esteem.
1 Figure out why you feel this way..
2 Give yourself permission to mess up..
3 Don't take yourself too seriously..
4 Change your negative thought to a positive one..
5 Re-define your idea of intelligence..
6 Focus on the things that you're great at..

How can I be smarter than my peers?

Five Tips for Becoming Five Times Smarter than Everyone Else.
Read. Constantly..
Get to know your internal clock..
Use a Notebook to hand-write your notes..
Use the memory tricks you learned in grade school..
Exercise! Both your mind and body need proper attention..

Why do I feel like everyone is smarter?

It's the classic sign of the Dunning-Kruger effect, a type of cognitive bias described by social psychologists David Dunning and Justin Kruger in which people believe they're smarter and more skilled than they actually are.