Uh, no. That is not an edge. That is poor risk management. Perhaps I have a different mindset, as I trade 100% automated. Every trade I make has an expected value based on statistics. Over time, a few bad trades, for whatever reason, become noise in the long run. I have measures in place to limit losses. Your point about an electricity blackout (any technical problem) is well taken. Redundancy is the key.
Some of the the advice is very good and used , but some advice needs to be filtered and ignored as it does not fit my mindset/personal psychology. Every trader has his own biases and traits and view of trading , he picks and chooses what to use. The 4 % is an entertainment thread to refresh things , it has knowledge benefits.
===================== Opro; The way , and or % size most of us traded ,while learning; our heads & hearts were right to be afraid. For example to [a] confuse trading trends with trading noise, confuse a bull or bear market ; [c]that should cause fear