addendum:
The elephant known as "Warren Buffet" in the room didn't even get mentioned here, although he did coin the phrase:
"Rule Number One: Never Lose Money. Rule Number Two: Never Forget Rule Number One", he did not 'invent' it.
The (my) logic behind this is quite simple (one of my (too many?) mantras):
"A Penny lost is a penny lost and can never be recovered".
For every loss one makes, one needs an extra win to cover for it and if you're Donald Duck, your deliberate losing aka "Risk-management" eventually will erode away on your Portfolio so much, the chance of recovery gets slimmer by the trade.
--------------------------------------------------------------------------------------------------------------------------
disclaimer number 2:
Never read the disclaimers or fine-prints .. EVER!
This, again, is trading advice. I am responsible for your (everyone's) losses and won´t hold up in court.