1. Not Determining your Stop Placement in Advance

You should know where your stop is going to be before you open a trade.
The same goes for your entry and target(s).
As soon as the trade is live and you’re seeing your p&l fluctuate, you’ll find every single reason in existence to stay in the market.
The benefit of ascertaining your stop before you open a trade is that it removes any emotions from the decision, because you haven’t yet risked any of your capital. You’re simply looking at a chart.
Additionally, if you don’t have a predetermined stop and the market starts moving against you with the full threatening force of big, scary Japanese candlesticks, there’s a much higher likelihood that you market puke the position without considering whether your trade idea has actually been invalidated.
There’s no point ‘winging’ your stop — decide where you’re wrong before you open a position.
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5 Stop Loss Mistakes To Avoid
Topic source: https://bitcointalk.org/index.php?topic=5162520