It will work, until it doesn’t. 
Our brains are pathetic at accurately judging probabilities, especially at the extremes.
Hopefully, one would have compared the expected-value of
the various investments with varying risks and rates-of-return,
and invested accordingly.
As an example, consider these 2 schemes…
- an investment scheme A
- a ~1% chance of losing the entire capital
- providing 9% returns.
- an investment scheme B
- a ~5% chance of losing the entire capital
- providing 14% returns.
…whose expected-value is the same.
Even armed with such a calculated approach,
there still remains some uncertainty/risk.
as one cannot accurately calculate/predict the probability of success/failure of most investments. 