Relax, enjoy yourself and have fun. Don't sweat it.
More practical advice:
1. Pools are less crowded in the morning and on port day.
2. If you are interested in character greets, there is a phone number to call. The advertised ones in the navigator get busy, the "unadvertised" ones you find out about from the character boards (one in the atrium, can't remember where we saw the second on) or the phone are less busy.
3. Don't forget to leave out clothes for the next day when you leave your luggage out the night before.
4. You may gain a little weight. You might want to work on taking some off before you get on the ship.
5. Check out the link above for links to recent Navigators to get some idea of how your days will go. These may change and the events probably won't be identical.