happened to me once. got big crush on one very good-looking guy
with cute dimples who could sing like Zhang Xin Ze.
he was attached but his gf treated him very bad.
we were great friends and i liked him alot.
so i wrote him a letter to tell him how i felt......... and also
added that it doesnt matter if he feels the same way for me.... my
intention, to let him know and me, to acknowledge my feelings for
him. it was what i felt at that time.
we didnt happen.... after that, i fell for and dated someone better
looking...... 
so what if you get rejected? may not be your problems for a start.
could be the other person has low self-esteem, emotional baggage,
is superficial or you are meant for something more.
just be true to your feelings. you can give things a shot and see
where it takes you.
that you owe it to yourself.
miss it and you may regret for rest of your life.