So you found a school you like
Be yourself: Yes, be yourself. You and your child cannot pretend to be someone else. If you do, someone other than your real child and yourself will get into the school. You cannot keep the show going forever. And what good is that? You want your real child to be taught. Not some image you create. Being yourself will give you poise and confidence too.
Trust the school: If you like the school so much, have faith in its processes. Trust that admissions folks are doing their best, what they are meant to do, whatever that is. Trust it. Your faith in the school starts now, not once your child is in the school.
Build a relationship: Focus on building a (not over-the-top annoying) relationship with the school. Get to know them. Let them get to know you. Your relationship built now will carry you into the future — at the school or back again when you reapply. Focus on that. This will keep you in the process instead of hanging on to the prize at the end.
Be calm: Your heart might be tied up like a pretzel but know that coming from a place of fear will only make you less appealing, less someone folks what to be around. Know and accept that much of the admissions process is out of your control. You can only control what you can. So, put your best foot forward and let go of the rest. If it is meant to happen it will. And when it doesn't it is for some very good reasons.
I'll close by saying — have faith yourself. If you see the connection and you are yourself, the school will too. Good luck! Good cheer to you this holiday season.