Don't leave any stone unturned, You wont be able to convey anything again, so make sure that you say everything you have too. Mention the good and the terrible, for me at least, my note is the culmination based on how I see it from my perspective. People dont know how you see them, so personally, in my note, I am telling them. Don't feel pressured by anything or anyone, it's very reassuring to know (at least for me) that this is finally writing someone cant critique. Good Luck :) I believe in you!