There are so many influences on planning a wedding, it can easily feel like you no longer have control of your dream. Wedding planners, caterers, the rules of the church or venue, the in-laws, and dozens of other distractions can impact you. Then there is the bringing together of all of the different factions. There will be those who may get along fine and others who don't, those who think your wedding is about them.
It can seem like there are two different types of people who surface at any wedding: People using their Big Brain (thoughtful, helpful, generous people who will do anything they can to make sure you have the day you want), and people using their Little Brain (emotional, selfish, impulsive people who think this day is all about them, and that your wedding is just another opportunity to tell people what they think).
Before any wedding, it would be wise to list the people whom you think may use their Little Brains and deal with them up front. We all have an uncle or an aunt or those certain people we know will use a gathering as an opportunity to act out. There may be some who have left-over baggage with others and see your wedding as a way to show off or get even. Once you have made your list, show it to your soon-to-be spouse and decide who will "have that conversation" with each of those people. You will communicate better with some, while your spouse will communicate better with others.
Long before the wedding, take the time to remind them that this is your day. Speak with them one-on-one to emphasize how they are a part of making your day successful. Telegraphing, ahead of time, what you expect of people can often take away that anxiety of not knowing what they are going to say or do. If people have enough time to process your wishes, it can make all the difference.
In the days leading up to the wedding, reconnect with them and remind them how important this day is for you. Thank them for helping to make this your day. For them it's just another wedding, but for you it is your one opportunity to have this ceremony with this person.
Weddings create a certain energy. Once the momentum is started, it is almost impossible to stop. It draws out the best in some and the worst in others. Add too much alcohol to the already-simmering tensions, and the chances of an incident increase.
You and your spouse have a lot at stake, you have so many other details to deal with and having to communicate to those who will potentially use their Little Brains seems like an unnecessary annoyance. But left to their own ideas of what the day should be, those Little Brains will always think it's their wedding.