In the time that I've been teaching English, both in Spain and in other countries, I've found that almost all of my students hate writing. It's easy to understand why. Effective writing (not just spelling, but constructing arguments and convincing people) isn't easy to do. Students also don't like to spend lots of time trying to write something that sounds intelligent...and then get a paper back that's full of mistakes.
One of the best ways you can avoid the disappointment of getting a (heavily) corrected essay back is to check for mistakes before you submit your text to your teacher. Many (if not almost all) mistakes are easily avoidable, and if you go back and look at the kind of corrections your teacher made on your essays, you'll probably find that you're not making a lot of different kinds of mistakes...you're making the same mistakes over and over and over again.
If this is the case, here's a downloadable writing checklist that can help you revise your writing before you submit it.
This isn't a list of every possible thing that students do wrong, but it does cover the most common (and the most easily prevented) mistakes that teachers tend to see. If you're writing the First Certificate exam, these are the kinds of silly mistakes that make students lose points and risk failing.