In my early days on an institutional trading desk, it was drilled into me that you don't make money when you exit a trade... you make the money based on how well you enter a trade.
Early in my trading career, I was once told that the only price that matters in a trade is your exit price.
Finally, in the course of reading 100s of books about trading and risk management, I learned that many old school traders think the only relevant price is your stop loss price.
I believed each of these theories for a time... but only a time.
I have since come to understand and accept that all of the prices are relevant and exceedingly important in their own right. While I believe that your average stop price and its size relative to the size of your winning trades is truly the most important, the other 2 prices carry special weight as well.
For example, the better your entries based on your setups, the smaller your risk can be, because you bring the all important stop loss price as close as possible to the entry price.
Similarly, your profit taking exits are an important part of the trading equation. Put simply, the better your trade exits [i.e., the further away from entry], the better your trading will be.
Take a look at the video below for an example of how I think about day trading exits.
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And the follow up in the afternoon to show what happened.
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