Risk Management. The way to be a better trader than a child with a coin

Thoughts about trading style, risks, money management. 

Somewhere I've seen video about trading in terms of probability theory. It was about a child, throwing a coin to get heads or tails and make Buy or Sell orders accordingly. In a such conditions, with 1:1 RR - child will have 50% win ratio.

Meanwhile - most trading statistics announces that less than 20% or even 10% retail traders achieves positive results, while the rest are losing money. So... we have clear view that a random child has better trading psychology (none) and better technical tool (coin) compared to most of traders...
How can it be? 
...with such a rich variety of courses, strategies, indicators, and robots...
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