Myth #4:

"As a beginner, you're bound to make a lot of mistakes"

This is often given as justification of the "Mistakes are OK" myth. The reasoning is that mistakes are a part of learning, therefore it is pointless to try to avoid them.

Fact:
While you cannot eliminate mistakes completely, you can speak and write with very few mistakes, even if you are a beginner.

The trick is to put input before output. If you follow good examples (i.e. build your sentences out of correct phrases and patterns that you have read in books or heard from native speakers), and avoid "uncertain" phrases (phrases that could possibly be incorrect), you will make practically no mistakes.

Here's what this means:

• You should not open your mouth until you see/hear enough correct sentences to build your own sentences correctly. If you can't help but make mistakes, spend all your time on getting input (reading and listening).
• You should look things up on the Web and in dictionaries before you write a sentence, to make sure it's correct.
• If you're not absolutely sure and can't check if what you're going to say (or write) is correct, don't say (or write) it. Otherwise, you may teach yourself an incorrect phrase.
• When reading or listening, pay attention to details like word order, articles, prepositions, and tenses. Compare sentences in the foreign language with equivalent sentences in your native language. Notice how different they are. This will help you realize which parts of your own sentences can be wrong.

The above techniques help you avoid developing bad habits that would be very difficult to cure later on. If you are careful and patient enough, you can learn with very few mistakes and gradually acquire the ability to use more and more phrases that you are absolutely sure of, until you can express anything you want in the foreign language correctly and fluently.

Further reading:
How to avoid making mistakes in English
"The best way to learn a foreign language is to speak it"