In forex trading every time you place a trade it is similar to solving a problem in an exam and hence, if you have done enough practice in home similar type of questions before attending the exam, then chances of you finding the solution is more likely.
Similarly if you have done enough practise on past data using your forex trading system, then chances are there that you will succeed in forex using your system. But if you have only read before the exam, but not done any practise, then even if you know everything you may fail in exam. Same way even if you know everything about forex, you will fail while real trading if you have not back testing.
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