The Holy Grail of Investing

In a recent podcast, Ray Dalio explained what is in his opinion the Holy Grail of Investing: 

"The Holy Grail of investing, the thing I have learned and it’s the most important is that if I can have 10 or 15, ideally 15 but even if it’s 5 good uncorrelated bets, that`s the Holy Grail. So, the Holy Grail is 15 good uncorrelated bets. (...) Knowing the value of uncorrelated bets is incredibly important. "