I've been writing fiction since about the sixth grade.The earliest memory I have of actually sitting down to write a story that was not for school was a story about a magical school bus that travels through time via the Space-Time Continuum. Of course there was nothing scientific about it, but when you spend more than half your time on writing--fiction or otherwise--you pick up on a few things about life. Three of these, I think, apply very well to life.
Read everything.
Absorb as much information as you can--it's going to come in handy someday when you get on Jeopardy or decide to have your protagonist walk down the street, fall down a manhole, and then wake up in 1365 AD in a barn on a haystack somewhere in Europe. When you write fiction, you are reliant on the knowledge you have and when you don't know something, you research the needed information. The same concept can be applied outside of fiction writing--essay and research papers for college are a perfect example. When you write a persuasive essay trying to convince the reader that they should learn basic outdoor survival skills, you will need that information if you want to get that big fat A+ with a double smiley face.
Believe in yourself.
Writing is a creative outlet that relies heavily on your imagination and creativity. And when writing a story or poem, it's not uncommon to think that your writing sucks. But you can't let yourself fall into that hole--the first draft always sucks so. After you reread that sucky draft, you note that the story has great potential, you just have to nurse it and raise it into a competent and epic story. Just like you have to believe in your writing, you have to believe in yourself and your abilities. If you want to become the top fashion designer or the CEO of a Fortune 500 company, you have to brush the dirt off the back of your pants and start running. You won't get anywhere if you just sit there like a giant zit in the middle of your forehead.
Take a breather.
There are times while writing that you find yourself on a roll--knocking out scene after scene that when you happen to glance at the clock, you find that you've been sitting in bed typing for the last ten hours. While you're racking up that word count and getting that epic time-warp manhole story finished, you're sacrificing much-needed rest. And after you crash, when you recover, you might find that you can't find the words for your story. Take a step back, stretch, eat, go for a walk, and rest before you get back to the grind. The same goes for when you're studying or working. While it's an admirable trait to be a hard worker, you don't need to work yourself into the ground. It's bad for your health. When start working without taking the needed time to rest and collect yourself, you will make yourself sick. Always remember to take a breather.