I know that many brides will want all of the details of their wedding done in a specific way, but sometimes you have to make concessions and compromise. Maybe it's a budget issue. Maybe there's a detail that you're not so concerned with but it's really important to your mom. Whatever it is, before making any statement you'll regret take a breath and walk away from the discussion and really think about how important this issue is to you.
Maybe after thinking about it you'll realize that it's not so important or maybe you can find a way to make a deal on another detail -- kind of a barter.
At my wedding I really wanted a 7-tiered wedding cake but my dad said he would only pay for the 5-tiered cake, and at the time I was really upset about it, but after the wedding I realized that the 5-tiered cake looked great and it was better in the end not to spend an additional $2,000 on the cake. Instead, I put that money toward a vintage Good Humor ice cream truck.
So before you fly off the handle because your groom is insisting on bottle opener wedding favors or your parents are insisting on inviting 30 additional people you've never met, ask yourself how important are these details to you in the grand scheme of things. And if you give into their request, remind them that you did when you are asking for something they think is ridiculous.