Mistake 4: You reach an agreement quickly just to end the discussion.
If you're not comfortable signing a prenup for whatever reason, don't. You don't want to make it something you know you'll regret later. You shouldn't agree to it just to end an unpleasant discussion, or because your or your partner's parents want you to. That will likely lead to bigger problems down the road, and you should make a choice you're both 100 percent comfortable with.