I had the amazing experience of working as a production assistant on a TV show in Los Angeles. I learned so many things about film and production, but also about life and people.
1. Hard work is the only way to be successful.
This sounds cliche, but it is true. Every single person I met on set had worked so hard to get there. If you took advantage of the job you were given and didn't live up to expectations, you're out. No exceptions. Everyone needs to pull their weight and give 110%. That's how the real world works. It doesn't matter if you're tired or don't want to do it. You need to suck it up and get work done. Knowing this and having this work ethic installed in me already helped tremendously.
2. Not everyone is nice.
I knew this already, but it can still be a bit of a shock to see negativity first hand. Everyone on set was very helpful and so nice, but pedestrians and normal people while we're working on location, not so much. Just because you are nice, helpful, whatever positive adjective you want to use, doesn't mean everyone you meet will be. That's ok. The best thing you can do is smile, continue to be nice, and learn from them.
3. You can only count on yourself.
This lesson goes hand-in-hand with the first one, but never count on anyone but yourself to get the things you need to be done, done. Not everyone has the same work ethic and goals as you do. They might not weigh the same tasks as heavily as you do in importance. If you have any tasks given to you, do it yourself. Never play the blame game, it's too tiring. Just do what you need to and sleep well knowing that you did exactly what you were supposed to.
4. Networking is key.
Chances are, your first job/internship isn't going to be a position you want to work in for the rest of your life. Get to know the people you are working with and make connections. These people can see your work ethic and personality and may be more inclined to help you out in the future. Even if they can't help you in the sense of a career, you now have a new friend.
5.No one cares about the things you're worrying about.
I don't mean this in a negative way, but no one cares about you. They don't care you have a pimple or that you're having a bad hair day. They care that you are doing your work. I know, for me at least, that this was a lot of pressure taken off my shoulders. Not focusing on what other people think and allowing myself to be completely engrossed in my work was amazing.