Interesting article that talks about things every 18 year-old should know.
http://zenhabits.net/2008/02/20-things-i-wish-i-had-known-when-starting-out-in-life/I think this is my favorite one:
11. All that stuff that's stressing you out — it won't matter in 5 years, let alone 15. When things are happening to you right now, they mean all the world. I had deadlines and projects and people breathing down my neck, and my stress levels went through the roof. I don't regret the hard work (see above) but I think I would have been less stressed if I could have just realized that it wouldn't matter a single bit just a few years down the road. Perspective is a good thing to learn.