Personal observation over a long trading career (started early 1990's) combined with learning about the prior trading history of many of my new clients (175+) that I have worked with over the years.
The term "Trade Management", tossed around like a shallow cliche, is treated with mock reverence. From what I've observed it's little more than a brief afterthought in aspirations of new trading system designers.
I have learned that the vast majority of aspiring traders spend 95% of their energy and focus upon trade entry and the management of said position just gets one or two cursory rules that are frequently overridden by "discretion". Too many new traders just "wing" trade management - it's a case-by-case gut call.
But it's trade management that ruins traders, and not trade entry. In fact, traders should pass on entries that by virtue of the range or volatility conditions will not accommodate a hard stop-loss.
It's just unrealistic for any new trading system designer to assume that a real trader in real markets using legal methods is going to consistently have even a slim majority of his trades that are never underwater. That is reality.
Just my 2cents, because I was asked.