I've been living with teens for about 6 years now. And while I thought it was my job to teach them, turns out they taught me a thing, or three.
1. I don't have to be liked to be loved.
My younger teen looked at me, at our final college tour, and said, "I don't know how, but EVERYTHING you do is annoying." This wasn't my first rodeo so I took this comment lightly. I texted the quote to his older brother who laughed heartily and said, "I remember those days, it will pass." I left him alone, not 15 minutes later we were sitting together laughing at the dinner the table. Teens teach you ARE annoying AND they love you anyway.
2 Control Doesn't Make a Grown-Up
Too much control can make us feel like good parents, that our kids our safe, that they will have a straight shot out of adolescence. Turns out, too much control makes you tired and angry and makes them sneaky and rebellious. Now, we can't give up. We still need to provide teens with firm boundaries and appropriate limits. However, control isn't an insurance policy and doesn't teach them much except how to work a work around.
3. I Don't Have All the Answers
Once I got used to this one, it was very, very relieving. I don't know the best way to get homework done. I don't know how tired they are. I don't know their interior goals. Now, it's taken me these full 6 years to start correcting my OWN righting reflex (the reflex to comment on every darn thing someone is doing and how they could do it the teeniest bit better because you really love the person). My instinct is still to tweak how they do stuff, but sometimes I catch myself BEFORE, sometimes during, and when I do it after, I can apologize.
3.5 Teens are Hilarious & Insightful
I love that you can let your guard down with teens, watch edgy tv shows and movies, share in discussions of current events, and generally they crack me up. I've also found that my teens know me very well and can offer up insightful advice to me. Tweak a decision of mine to make it better, modify a reaction to be a wee bit more sane and deliver it (mostly) with a sense of humor so I can receive it.