Amy, I love your letter and think it contains quite enough as it is. The only thing I'd be doing now is chopping it down, editing for brevity. You'd be surprised how many extra words you've used. eg
This understanding has contributed to my determination to learn as much as I can.
could be cut to
"This understanding has made me determined to learn as much as I can."

Less wordy = more likely to be read through to the end.

I'm sure your application will be accepted, first round !