My best advice is to take it one step at a time. Thinking of the entire trip is daunting.
One step at a time, then ask someone in a uniform if you have questions.
"Excuse me, can you tell me how to get to gate 48?"
"Ma'am, do I have time to run to the restroom before we start boarding?"
You basically know the drill, so nothing will be entirely new to you. At 19, you are starting to convert from dependent child to independent adult. This is just one step along the way.
Stay organized, stay alert, avoid alcohol and you will be fine.