Most probably it is because you are not aware of the basic rules of English and is learning from the wrong sources.  I hate to think that it is due to sloppy typing.  First of all, 我 = I.  No exceptions.  Your capitalization is non existent, your punctuation spacing are all wrong.  Finally you are using slang instead of using proper English in an essay.  Most probably you have been writing too informally in chats and emails that you are so used to them that you cannot differentiate the proper ones.  Even you used the slang wrongly.  No wonder your teacher chided you.  You really needs much help to steer you to the right course.

I am really poor when it comes to my writing.  Usually my teacher chided me that I used wrong words, grammar and tenses.  My critical and logical thinking are lacking.  Should I say my mind goes blank when I have to write an essay or article.  How should I go about to improve my status.

P.S.  Writing essays for TOEL drives me nuts.~!@#$%^&*

i do really poor on writing, usuaully my teacher said i used wrong words, grammar,tense...

i m lack of critical thinking n logical thinking,or say, my mind goes totally blind when i m required to give an essay or article. how could i do with that ?
p.s. TOEFL writing part makes me go nuts!
~!@#$%^&*