Mistakes are not harmless. Every time you say an incorrect phrase

in a foreign language, you increase the probability that you will say that phrase again. Therefore, if you speak with mistakes, you can easily teach yourself bad grammar.

A lot of people think it’s more important to improve your fluency than to improve your correctness. If you follow this path, after some time you may find you can speak the language with ease, but it will be largely your own version of the language — not correct language as it’s spoken by native speakers. In other words, you may become quite fluent in speaking the wrong way.

Source: Antimoon

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