The bride is the star. Whatever problem you are having with your hair, make up, dress or attitude in general is not her problem. Settle for the best you can do with yourself and keep the attitude in check. She needs someone to keep her spirits lifted during the countless things she will worry about through her special day. If she can manage this day and make wonderful memories thanks to the positive attitude you kept it will mean the world to her. She will remember how much love you poured into her special day and how many pits she avoided thanks to your help.
Once you have managed to get through the planning and the ceremony it will be time for the party! I can tell you as a coordinator that this is the moment that I sit back and smile. Everything is in place and my beautiful couple is married. All of the worries they have struggled with have dissipated. It is a blissful moment when they realize what is most important, the love they have for each other and their families who are there to celebrate the moment with them.
It is also the time that my team and I start to watch the wedding party closely. Most of the time there are no issues but when there are issues, they are generally due to alcohol consumption. If you are a member of the bridal party it is very important that you are very careful not to think of this as a night to drink like you would out at the club. This is a time to celebrate within reason. You do not want to have the unfortunate experience of embarrassing yourself and your dear friends.
You are a very special part of the bride's day, treat it as such.