Why do I think of her?

I have this special friend, Katie, and recently, I've just been thinking so much about her...

She's beautiful, yes, funny, and very comforting... but, at the same time, its like I've known her for roughly 3 years, and I just recently acquired these strong feelings for her, like I want to be the one man she can count on.

I don't know of the likelihood of an "us," as she may see me another way; but, I'm definitely willing to try.

Has anyone ever gone through this? Also, what do you think of it?