I know
exactly how you feel,
Kestra. In my field, I am almost always surrounded by stunningly brilliant people. Now, I know I'm pretty smart (actually, more than that), but sometimes I feel embarrassingly slow compared with some people in my department. Intellectually, I accept that, but sometimes the feeling can get pretty overwhelming.
How do cope with it? Well, first of all I had to develop an unshakable confidence in my abilities and worth. Even when I fail to understand or accomplish something, I never let it chip away at my confidence. I flunked? I'll do better next time. I fucked? I won't do it again. You have to find the source of your inner strength, and tap into it when needed.
Then, know your strengths. I may not be the sharpest pencil in the drawer when it comes to quantum mechanics, but I swim in general relativity like a barracuda in a river. And even when my programming mojo fails me and I have to ask for help on that, I have people coming to me to translate a particularly idiomatic passage in English, or to read their report and help them to word it better and more clearly. So, find the parts of your job you do best, and latch onto them.
Last (but not least), your job is not your life. Even if you feel you are lagging behind in your studies or tasks, that's not the end of the world, nor a threat to your worth as a human being. I know there is a tendency, especially in today's extremely competitive world, to equate a person's worth to their job (or their wealth). But you are who you are, not what you do. Even if you are experiencing difficulties in your job, there are other part of your life that usually make up for that: family, friends, spouses, activities.
I may not be the most brilliant cosmologist in town, but when I think about it: I have a lovely fiancée who loves me, lots of friends who enjoy my company, a family that stands by me, I am happy to pursue activities outside my job, and I am in general an awesome human being. I'm sure you could find the same in you.
Also, sometimes I find it useful to venture outside my ivory tower and talk with the mundanes, to remind myself that, even if I'm not the smartest guy in my field, I am still several orders of magnitude smarter than most people outside of it. That's a pretty big boost for my already super-sized ego.
