If you ask "How can I learn to speak English better?", many people will tell you "Practice, practice, practice". "Speak and write in English whenever you can" — they will say. All English classes are full of activities which involve speaking and writing. You produce sentences when you do an exercise in your book, when your teacher makes you speak in class, or when you have to write a composition. All these activities are supposed to help you with your English.
We agree that practice can be very useful. It's even necessary to learn English well. So what's the problem? The problem is that for many learners, "speaking" or "writing" means "making a lot of mistakes". Some people make a mistake in every sentence!
If you don't make many mistakes, then you can speak or write in English and it can only help. But if you make many mistakes, then every time you write or speak, you reinforce your mistakes. As you write or speak, you repeat your mistakes constantly and your incorrect habits become stronger.
Imagine this situation: You are writing an e-mail message in English. Your English is not perfect and you want to write the message quickly. You write (incorrectly): "I want speak English."
When you write a sentence, you also read it. So the incorrect sentence goes into your head. The next time you write a message, you will be more likely to write "I want finish" or "I want be happy". Why? Because "I want speak English" is fresh in your head — you've just used it! And when you write "I want <do something>" the second time, you've got a "bad habit", or a reinforced mistake.
Now do you see our point? You write — you make mistakes — those mistakes become your habit, they become your way of writing in English. So, the more you write, the worse your English becomes.
Stop making mistakes! 
We have said that you need practice to learn English. We
have also said that when you practice, you reinforce your mistakes.
Mical suggests a simple solution to this paradox: Never make mistakes! Here is what he says:
It is close to the truth that I have never written an incorrect English sentence.
I knew many grammatical structures and I used only those that I knew. My sentences were similar to sentences which I knew to be correct. I followed good examples, so all my sentences were good.
In the beginning, I could write only very simple sentences, but all the simple sentences were correct. Then as I advanced, I added more and more complicated structures, and again all my sentences were correct.
Because of this approach, I was never reinforcing bad habits. I never had any bad habits! From the beginning, I copied only correct sentences. With every sentence that I wrote, I reinforced my good habits.
You can speak and write with almost no mistakes, too.
You may be thinking...
"But practice makes perfect!" 
If you make many mistakes, speaking and writing is not the way to eliminate them! On the contrary, it reinforces them, as we have shown earlier in this article.
You have to realize that speaking does not improve your grammar or your vocabulary. It's really very simple. Can you learn a new word from yourself? If you don't know how to say "Good bye" in English, can you invent it by yourself? No, you can't. You can only learn it by reading or listening to English.
Or take a language you don't know (e.g. Latin). Now try to learn Latin by speaking it right now. Come on, speak Latin! Don't be shy. Practice makes perfect! — Obviously, you can't. Why? Because you need to see some example Latin sentences first. We hope we have shown that the main way to learn a language is to read and listen to sentences in that language.
So what should you do if you can't help but make mistakes in your English sentences? If you make mistakes, that means you don't know how to say things in English. You need to learn how to say them. You won't learn that by speaking or writing. You must read and listen to correct English sentences.
You can speak and write later — when you can already build correct English sentences and want to improve your fluency (your speed).
"I'll get better by practicing, because my teacher corrects my mistakes!"
Perhaps you can benefit from corrections if you get a few corrections per week. But when there are many mistakes, you become unable to concentrate on them. If a teacher returns your composition with 20 corrected mistakes, how many of these corrections can you keep in your mind?
Besides, your teacher is not always there. What if you're writing an e-mail message on your own or talking to someone else? Other people usually ignore your mistakes, and even your teacher does not point out all of them.
The conclusion would be that fighting your mistakes is not easy, so it's better to avoid making mistakes altogether. 
"But if I'm afraid to make a mistake, I will never open my mouth!"
First, try to be more careful by using the rules of error-free speaking. If you still make a lot of mistakes (= more than 1 mistake every 3 sentences), or if you find that the rules are killing your motivation, you probably shouldn't open your mouth just now. Instead, try to get more input by reading and listening in English.
"But you can't learn anything without mistakes!"
True, but believe us — you can learn English with almost no mistakes. How? You can fill your brain with correct sentences and imitate them. You can simply follow good examples.
If you write or say sentences that are similar to correct English sentences (from a book, a dictionary, or heard from a native speaker), then it is very hard to make a mistake!
"Can I ever make a mistake on purpose?" 