I didn't really calm down until a new friend I had just met (who had just returned from his mission the week before) was explaining how many blessings and feelings of peace come from the Temple. I had another friend tell me before I was baptized to "Get your Temple recommend as soon as you possibly can, and go to the temple as much as possible.
That couldn't have been better advice. I won't go into too much detail, (it's sacred, not secret), but I will say this: I have never felt more close to Heavenly Father than while I was at the temple. I encourage you to bring a notebook with you to journal while you are waiting. Those are memories that you don't want to forget. I haven't been back since April, but I know that I want to go to the Mesa, AZ Temple when I visit in May.
It is the most beautiful temple I think I've seen thus far! (In my own opinion of course!)
The least you need to know:
1. Don't be scared, it is the house of The Lord! :)
2. Don't be afraid to ask your ward members or members of the bishopric if you have any questions about the day.
3. WEAR WHITE UNDIES!!! If you are wearing a headband, or hair ties, make sure that they too are also white. Most temples have hair ties/headbands to borrow :p
Me personally, I would rather have my own..
4. Bring a notebook to journal with! TRUST ME. You will want those memories later in life.
5. Pray. Pray before you get there, and pray after you leave. It is a great way to usher the spirit into your heart.
6. Take some pics!! It IS your first temple trip after all!
I know that the blessings are IMMENSE. You will find that as you attend each session! Happy Mother's Day everyone!