I think you're right that if you throw in all your achievements that it could put others off through sheer intimidation!
Aside from being confident, how else do your friends describe you? Do you have a great sense of humor? Have a tough outside, but gooey inside?
I think a good write up would include some of your achievements, but also some of your quirks and the traits that make you a good friend. I wouldn't spill everything about yourself, but hint at some things to intrigue people into wanting to know more about you.
Something like:
"I'm a bubbly gal who likes to play Guitar Hero for hours on end, but in my spare time I earned a masters in education and like to teach disadvantaged children. I am a regular at my church, enjoy learning new dishes to cook up, and like spending time at the beach doing outdoor activities whenever I can."
(Note: this is
not a description of me!

)