YOU'RE the centre of attention on the biggest and best day of your life. Everyone loves you, and the whole world smiles on.
That was my wedding day, a long, dark time ago, and it'll be just the same on yours, except with a RAF flypast and a global audience of billions.
You'll have realised by now there are some traditions you just can't shake. The in-laws want their friends on the guest list, everyone's got an opinion on the honeymoon and there's a table of dodgy types you have to seat as far away from granny as possible.
One of the rules is that those who have survived the institution reminisce about their own nuptials and feed unwanted advice to the happy couple. But the one thing they don't tell you is the most important - that the wedding doesn't matter a damn.
It's once the ring goes on that the hard work starts. A wonderful wedding doesn't mean you don't get a miserable marriage, and when I was the same age Kate is now I was starting a divorce.
While I admit that I don't know the first thing about how to have a happy relationship, I do know exactly how to screw it up. So for what it's worth, here is my twopenn'orth:
1. Marriage is a 50-year project. Don't sweat the small stuff.
2. Always check his pockets; do not let him know you do this.
(Men will not like this advice, but if something bad happens at least you're not surprised. Being surprised in a bad way is, believe me, the worst kind. All men reading this will now ask their partners if they check their pockets/phone/email and she will say "of course not". She is lying. And if she didn't check before, now that you've asked her she will.)
3. You will never be this thin again unless you develop an eating disorder or get divorced. Enjoy and accept it, because you really don't want either of them.
4. Get rid of the dress. You'll never wear it again, whatever anyone says, and it will hang in a wardrobe wrapped in plastic "in case it loses the magic". My groom spilt beer all down mine, something I still haven't forgiven him for, and yet I refused to get it dry-cleaned in case it was "ruined".
5. It's called love-making for a reason. If you stop doing it, you stop feeling it and the whole wall comes tumbling down without that cement to hold it up.
6. Be quick to say sorry, and slow to blame. Be nice to each other.
7. Do your own thing. You've got two feet, so stand on them, and let him stand on his. You're not a doormat or leaning-post and nor is he. You walk side-by-side down that aisle; no-one gives anyone else a piggyback.
8. Never tell a lie, even a white one. You always get found out in the end and it only leads to more lies. Frankly it's too much effort.
9. Love is like a tide. It comes in and goes out, and just because it doesn't always feel like it did on your wedding day doesn't mean it's gone. The best advice I ever heard was this: "Marriage is like a stick and you each hold one end. Sometimes the stick is short and you're close together, and other times it's longer and you can't even see the other person. You just have to hope they're still holding their end of the stick."
9. a) Don't drop the stick.
10. There has never been a Prince of Wales in history who didn't have a mistress, as your future father-in-law so famously said to his first wife. Think about that before you put the ring on.