What should every stock market investor understand about risk?
#1 - Risk taking is part of the game. If you want ZERO risk, stop trading. Risk is how you ”attract profits”. Take smart risks and minimize your losses.
#2 - You can decide how much money you are willing to risk on each trade and how many open positions at once.
#3 - You can’t determine where the market will go in advance, so follow your own rules — your time-tested personal rules (mentioned in #2 above) to keep you from making bad/emotional decisions which may expose you to even more risk.