Because a lot of different people will have helped you with the planning of the wedding, and because they want your wedding to be perfect just as much as you want it to be perfect, these others will have a tendency to become overbearing on the day of the wedding - but it is important for you to remember (and even for you to remind them if necessary!) that it is your day, and not anyone else's!
On your wedding day, it will also be very easy for you to end up getting stressed, as you will want everything to be perfect - but by the time the wedding day rolls around, you will need to force yourself to realize that you cannot change anything, and you may as well enjoy everything just the way it is.
And finally, you will want to make sure you pay attention to the words and advice of all the people who lament the fact that their wedding day "went by too quickly" and that they "hardly remembered a thing"; for most people, the wedding comes and goes in a whirlwind, so make an effort to slow down the day enough that you can enjoy everything that is going on!