Enjoy this time where you can sleep whenever you want.. You will be way more tired when LO comes, you will think the day will never end, and believe me sometimes it doesn't. But enjoy this time to yourself.. Forreal..
To keep calm, I'd say make sure you have everything in place. Get all the things you need so you aren't stressing at the last minute. Just relax, like everyone else said - enjoy this time while you're still by urself.