Quote from nitro:
I don't agree with this attitude at all. When you can get a mathematically correct computation that does the right thing, you want to use it, even when you are trading discretionary. But the point really hits home when you are trying to implement an automated trading strategy, then it becomes critical that these questions be asked and that what you are doing is mathematically sound, or at least trading sound.
nitro
Fair enough - I tried to make it too simple so no wonder it kicks back.
It is obvious that for some types of trading (like black box) you may need to backtest what fits the best a particular strategy. That is however a different question to if you should or should not scale in/out. That decision comes before the black box is set up. I should disclose however that I do not run a black box (I trade <i>discretionary</i> global macro) so my experience here is limited.
My point in the above post was that you can be a successful trader only when you enjoy yourself (and not have soft shit all year round). Everybody is different so scaling in/out and the extent of it depends what your experience tells you what makes you happy (<b>given the implied odds!</b>) Somebody may be less risk averse and let the position run (making the outcome more volatile), somebody value lower volatility of outcomes more and averages up/down.
Personally I like to have core position that I let run and trade around it, i.e. scale in/out as shorter time horizon suggest with keeping some minimum floor position as long as I like the odds. I like to consider this type of trading as kind of psychological insurance - if I scale out and it goes up afterwards I still make some money...
I value interviews with successful traders but I value my experience more than theirs - exactly because it is <b>my</b> experience. I say it because I do not believe in universal truth in life (and therefore in trading).
