Sun Tzu's eight rules for gauging the erosion of our current positions.
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This article starts by explaining that positions erode slowly so is easy take our positions for granted. We tend to over-value exiting positions as they decline over time. We base our judgments upon the past. We find it difficult to see a gradual decline. We defend an existing position simply because it is ours. As a position declines, we continue to investing in its maintenance even when it is no longer returning meaningful rewards. Past success doesn't mean future success, but the more successful a position has been in the past, the more we tend to invest in it whether those investment pay off or not..