It's likely that the two of you are going to get into more arguments than usual during this three-week period, or at least some heated debates, because suddenly, you're both standing behind your own opinions as if you were defending your own body. Neither one of you is in the mood to back down, either; if an argument starts, you'll both push things to the limit just to have the last word. That's no fun, so do try to keep a sense of perspective when conversations start heating up between you.
Even if you think you have to hammer a point home and make sure you were heard, it's still possible to take a step back and realize that that's really just your ego talking. On a more positive note, you're not just talking now; you're making things happen. That's why it's so important to avoid the potential for argument that this period brings; because, when you're working as a couple now, you can get an incredible amount done -- much more than you could have done on your own. But if you're too busy fighting, neither one of you will be very productive! So remember that you're on the same team, and work together toward the same objective.