Ugh. All. The. Time. i think it's less that i doubt what's happening inside me and more that i doubt my ability to present a clear, understandable version of this process to the rest of the world.
The worst is in the classroom; in my field of study we talk a LOT of theory, something i've always been great at. i know my ideas are thoughtful and would add a lot to the discussion, but in class i find myself doubting my ability to communicate these inner musings to the rest of the class. it's sooooo annoying because usually i will think of something, try and organize my thoughts, write it out so i have a reference....and before i know it the professor or someone else in the class has said exactly what it took me 5 min. to put into a coherent sentence.
My extroversion is rather well developed, i just find that there's SO much swimming around in my head it takes me a long time to catch up with all of it and cut out all the rambling bits. my writing skills tend to be much better, but even still have problems organizing my thoughts for others to understand.