High Returns-Low Risk Paradox

As a trader, it never occurred to me that the high return-low risk phenomenon was a paradox, yet most investors and professionals believe the relationship to be high return-high risk, and according to Pim van Vliet,

Most cases, you take risk, you don't get the reward, and that's an important lesson also for starting investors who think that risk is like Karma: you take risk and then you get the return. That's not the case.