Things I wish I knew before going on my first mission trip:

Your life will never be the same again: You will see things that will constantly take you back to your trip. You will think about your trip in some way, shape or form every day.

You aren't going to always like/agree with everyone on your team: Not everyone is going to be your best friend. This being said you need to learn to work with these people and put on your happy face every day.

Common phrases in the native language: It is helpful to know basics of the language, be able to carry on a simple conversation and use proper manners.

Know what is common for the area: It is important to see their world through their eyes. What is common to them may not reach the standard expectation you are used to.

Know when to step back and take care of yourself: You can't help anyone if you don't have your own basic needs taken care of first. You don't want to end up sick partway through your trip.

Be prepared to share everything: You are part of a team, if someone forgets their bug spray one day be prepared to help them out. Then next day you might need the favor returned.

Giving people a lot of things makes it difficult to know if they like you for who or for the stuff you are giving them: It's great at first to see the joy in people's after giving them something they wanted/needed, but it is hard to know if you have a true friendship or if people just want more stuff.

The first day is the hardest: You are tired from traveling, you're in a new place and normally not much is planned giving you a lot of down time to think and second guess what you have gotten yourself into.