I certainly do believe anyone engaged in the management of money should have a standard of measurement, and that both he and the party whose money is managed should have a clear understanding why it is the appropriate standard, what time period should be utilized, etc.
Investors, of course, can, by their own behavior make stock ownership highly risky. And many do. Active trading, attempts to "time" market movements, inadequate diversification, the payment of high and unnecessary fees to managers and advisors, and the use of borrowed money can destroy the decent returns that a life-long owner of equities would otherwise enjoy. Indeed, borrowed money has no place in the investor's tool kit.
Confidence in markets and in institutions, it's a lot like oxygen. When you have it, you don't even think about it. It's indispensable. You can go years without thinking about it. When it's gone for five minutes, it's the only thing to think about.