How do you think this will turn out?

Last night I had decided for sum unbeknowest mental problem I have I guess, that I was going to spill out my guts to this girl I've been in love with for almost 4 years. She's one of my best friends. I had tried to tell her how much I liked her but was a little bit sketchy about it due to my fear of rejection and made it sound like I wasn't sure about her a year ago. Then when she said she likes me back but doesn't think I'm right for her but is just attracted I got really discouraged, but later went out with a girl a few months later for almost a year, but then that didn't work out. So when I finally got over that girl and even while I was dating this other girl i still cared very much for her. So last night at church I was going to tell her face to face and hand her this letter where I just spilled my guts. That didn't pan out cuz I got real nervous so I sent her a message on facebook (probably negatvive points, i know, but not enough to harm my chances that bad, I could always patch it up by talking to her face to face tonight). Now I am freaking out wishing I hadn't sent that letter. She's already talking to almost involved with someone else. I used very strong words almost told her I love her in the message I sent. I feel like I'm going to be sick. What can I do to feel better about this? But now it's either crash and burn or soar with the eagles.