I agree , but if you have a good signal lets say for example RSI >80 or RSI <20 you would be tempted to capitalize on the move and not let go of the trade even if the market went againt you a little bit.

as an oversold could be more oversold , so it may take some pips before you get what you wanted, it all depend on the develper and how sure he is from his setup.

I am not in fav of martingles but I have a couple of good entries where I prefer to scale in or add more trades instead of having big SL, its just a matter of how bad you want to stay in that trade , some trades you want to let go and others you want to hold on to it

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