Had a similar problem through out my Academic life. Sometimes I wish I could have gone back with what I know now and done better.
No Idea how old you are or what your situation is, but for me I found my self easily distracted by Video games, Tv and Movies.
Probably because I always unrealistically felt that everything would magically fall into place and that I'd ace every test but never actually though about dealing with the issue until it was too late. Even now I'm procrastinating instead of going and studying for an exam in 2 days.
Just because you have a good brain doesn't mean you can do good on an exam without studying for it.
So I'll do exactly that right after Posting.
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When I was younger and hooked on scheduled TV (instead of streaming online) I had to keep a watch on when I went to studied and when I ought to take a break, I ended up wasting tons of time in front of the screen because it feels good to ignore the looming issue and postponing thinking about the work is easier than doing it at the moment and potentially sacrificing relax time. At the time I had no Idea what the future held, after all this was my first go at life.
I'd never completed school or gone to college yet, I was still in highschool. as such Ithough stuff would be easy I never realized the actual amount of work that the other kids pu in, after all they made it seem so easy.
and even when my little sis, who aced at everything studied, I ignored the fact that she used to spend the entire night working for an exam which wouldn't arrive for 33 days, and that she used to spen an extra hour at school to collate her notes before coming home and that she used to spend an extra 1 1/2 hour at noght before dinner and through out the evening studying , even on normal school days when no exams were in sight, she filled notebook upon notebook with notes and other stuff.
I used to spend all this time, like I though everyone else did, watching TV, playing games or hanging out with friends, after all my sis did these things too, yet she somehow did better, It was only later after graduation that I realized that my twin used to study in the empty spaces that I used to spend loafing around watching TV or reading a book.
she did those things too but only when she was free. I never truly comprehended what was going on in front of me.
Sure as a result she wasn't as knowledgeable as me about Trivia, or stuff going on in our favorite TV shows or about Comic Book heroes etc.
I knew far more stuff than she did about world customs and stuff not in the syllabus.
the thing is we each have 24 hours to study stuff. now like me you can either gather knowledge right now sacrificing your school syllabus or put learning and hobbies on a hold and concentrate solely on being a bookworm until you reach college and summer holidays etc. where all of a sudden there's ton of free time, and your sis suddenly catches up to you and now not only knows everything you do but the stuff you never bothered to study, and as a result is going to a better university.
Another reason I suffered was because I never thought it comfortable to ask teachers or friends for help, due to my false pride of not appearing dumb by asking questions or severe case of fear speaking infront of classmates, I rarely asked a question and it showed in my grades. as a result I had no one to turn to when I didn't get something and suffered thanks to it.
I also never realized that the friends I used to hang out with had very similar schedules to my sister. I never truly used what I saw in my own life for some reason.
You Cannot do the same.
Ignore what your parents have said so far. you future is now in your hands.
swallow your pride and fear, postpone all those tv shows and movies and games, dates and outings till you're 30. Find the smartest kid in your class, and beg them to help you, take your notebook with you and study, it will be hard and grueling, but for the next 4 years you will NOT be having any free time, you will have no life, all you will do is sleep, eat and study.
Resign yourself to this fate. write down all notes and read your textbooks at night. when the tests come they will be a breeze. do not wait for them to come close start studying as soon as you get the material, don't wait for teachers to cover the topics in class, you should have finished the whole book in the first few weeks of school, and even then when it feels like the best time to reward your self after having gotten ahead of everyone else, you may not, you must FORCE your self to continue with the studying.
Commit what may seem like social suicide by forcing your hand up even for the most stupid question(you won't know these people after you graduate, it doesn't matter what they think of your questions, your grades will redeem you).
ask the teacher for [seemingly bothersome] private tuition after class during break or after school or on the weekends(you will have NO free time) accept this bitter and difficult truth.
Life is not as easy as it looks, there's a LOT of work that goes behind achieving success. You must have confidence in your abilities and lots of dedication.
Sadly you won't be watching the Star Wars movie this December, you will also be disconnecting your self from all social trends and culture for the next 4-5 years. you can get back to all the stuff you missed after school is over.
Yes you will end up becoming a Pariah of sorts, with no Idea what your friends are talking about and completely out of touch with world news and what's popular. you will get good grades though.
I f you are extremely harsh on yourself you will eventually find actual free time, time where there's nothing more left to study because you've memorized and learnt everything. it will be during these rare gems that you can keep up appearances of being a normal human(meeting friends, watching TV with family, going out on a date etc.)
otherwise lock yourself up in a simple room, with no TV or books other than your study music and a lamp, and perhaps piano music or some other genre that helps you study.
check out http://cmd.to/fm
Work your butt off and you'll get there, it will be hard, very hard. near inhuman, but you MUST do it.
start now. I'll start in an hour (I'm hungry and find it difficult to take my own advice =P )