The BIG MISTAKE that can happen then is what? Well, it is the little thing called liquor and pills to help calm a person down. It is ok to have a little drink or if the drug is prescribed for to take one but, not right before you walk down the aisle. It makes for a messy ceremony and if it is being video taped a lasting memory of the things that went wrong on that day. You tend to forget how to speak, your eyes are glassy, and your walk is not as it should be. The officiant may not sign the marriage license if that person thinks that you are not at full compacity. Don't let your day be ruined by a little nerves and the wrong decision. Take time to breath, talk with your officiant, and know that people love you no matter what. It is your day keep it special.
Love and peace to you all.