Not let your vision get crowded by all the outside influences. It doesn't mean you have to be crass or a jerk to anybody. It just means you always know what your goal is and you always focus on it. Any person that is doing this, I think they would be making a great mistake in only focusing on the physical aspects of the sport. Even at 30 I'm trying to offend less people more of the time and figure out the best time and place to address controversial issues.
Nordic training is simple.
You just have to train a lot and train smart. You just have to take your time cause your brain will always push yourself harder than your body will allow. Trying to become an elite athlete is a really good growth tool because you are constantly evaluating yourself. That's not to say that you can't be good at school or other outside things. I encourage kids to get involved in other stuff.