I am motivated to serve as a Peace Corps volunteer for many reasons.
Throughout my life I have enjoyed discovering new things, overcoming challenges, embarking on new conquests, and achieving the goals I have set out for myself.
Too vague. This is true for virtually everyone.
The Peace Corps presents an opportunity for me to do all of these things in a brand new way that I have never experienced before.
"Brand new" and "never experienced before" are redundant. And, again, this is true for everyone applying to the Peace Corps, unless they've served before.
I could go on. The problem is that you don't answer the prompt with any specificity at all until your last paragraph and, even there, you tend toward vagueness. I'm afraid you're going to have to start over, being mindful of the need to answer the questions with specificity and detail.