hi edge, usually I use scheme, first I write three or four introductions at depen of formal or informal documents,for example, Mr, hello there, to whom to may concern or my Darling NAME, secondly , I write general sentences for writing diferents topics,letters,articles blog , in fact you can do a list with general sentences and them ,you write in the text this senteces and fill it with the words of topic. I use this trick in exams, I think that is important to read books and articles with the dicctionary in hand .you learnt a lot of Word for using in your writing.
I discovered italki days ago, and if you write in blog, you able to practise a lot of .
There is a solution for every problem. In your case you should take some English writing and composition classes. here is an example of a better way to compose the paragraph you wrote above.
I'm able to understand difficult text and I can speak English fluently. However there is something about writing English that I find very difficult. I'm sick and tired of this situation, please help me out! What am I suppose to do? I've lost patience, I've tried several ways to rectify this problem, but it didn't work.