Should you try to outperform the markets or invest in an index fund?

This is the best article on this I ever found:

https://ritholtz.com/2014/02/the-best-investment-advice-youl...

"Bogle’s closing advice was as simple and direct as that of his predecessors: those brokers and financial advisers hovering at the door are there for one reason and one reason only—to take your money through exorbitant fees and transaction costs, many of which will be hidden from your view. They are, as New York attorney general Eliot Spitzer described them, nothing more than “a giant fleecing machine.” Ignore them all and invest in an index fund. And it doesn’t have to be the Vanguard 500 Index, the indexed mutual fund that Bogle himself built into the largest in the world. Any passively managed index fund will do, because they’re all basically the same."

You do both. Put most $ into index funds, but put some percentage into your own stocks / other investments.