I have my own wedding pretty much completely planned out already. I know how old I want to be and what time of year - I even know what I want the invitations to look like. That doesn't necessarily mean it's all going to happen as planned, just that I know what I want.
I love that I know enough about what I want to know how I want my wedding to be. But that's not really what marriage is about. A wedding is just one day. A marriage is a commitment that lasts a lifetime (or should, anyway). I may know what I want from my wedding, but I have no idea what I want from a marriage. I mean, I think I want kids, and I want to be generally happy, and in love. But that's all I know.
I think that's okay though. Maybe some things aren't meant to be planned out all the way. Maybe life is better with a few surprises. I sure hope so.