This would probably shock most of our friends and family, but DH and I had two big fights in the months before the wedding where we yelled about not getting married. I also got so mad at him the night before we left for the wedding weekend that I called one of my best friends and was like "what am i doing??" Looking back, it was pre-wedding jitters that really magnified everything. I'm guessing (hoping) I'm not alone....
One of the best things my parents did during the wedding process was to tell me frankly that if at any point we changed our minds that it was better to lose the deposits and not go through w/ it (their best friends' son got separated two weeks after his honeymoon and basically said he knew he was making a mistake when he walked down the aisle but thought it was too late to turn back once they wedding was planned).