Quote from Ghost of Cutten:
Yeah, it's irrational to view house money as any different to initial capital. Otherwise two people with identical risk profiles, capital base, and positions, would have to trade the exact same market very differently, which is clearly illogical. Or if your clerk accidentally exited your whole position by mistake, you would not be able to put it back on again at the same price, which is again nonsensical.
Trend-following suggests that the expectation on a trend-trade is significantly better once the trend has got underway and made a significant move. Whereas at the initial breakout point, the chance of being wrong is pretty high. Thus it makes sense, purely on trade expectation, to cut losses quickly at the breakout point, but to be much more tenacious in holding through pullbacks once a good profit has been built up. None of this has anything to do with it being open profit vs initial capital, it is solely due to the (presumed) character of major trends (choppy and prone to failure early on, more resilient and able to bounce back from corrections later). However, some trend-followers IMO have not grasped this distinction, and thus use the psychological crutch of house money vs initial capital to rationalize the correct behaviour. A bit like a fighter pilot might check their six for superstitious reasons - their action makes sense but not for the reasons they think it does.