Warren Buffett emphasizes that while achieving success is exciting, effectively correcting mistakes when they occur is equally critical for businesses.

Berkshire Hathaway ( BRK.A -0.05%) ( BRK.B 0.24%) is considered by many to be a reliable stock for long-term investors. It's outperformed the S&P 500 ever since a young Warren Buffett took over the company in 1965, and its evolution from an aging textile maker to a diversified conglomerate churned out millionaire-making gains.

The conglomerate sold Apple shares during the second quarter, though the iPhone maker remains Berkshire’s largest stockholding.

Warren Buffett has cashed in a net $177 billion of stocks because he expects a downturn and plans to capitalize, Wedbush's Paul Dietrich said.

Berkshire Hathaway recently filed its second-quarter 13F form, revealing its stock holdings at the end of June.

Like Amazon CEO Andy Jassy, keeping a positive attitude helps the Warren Buffett-backed leader stay motivated toward success.

Buffett owned UnitedHealth shares before selling his stake in 2010, though his Berkshire Hathaway recently acquired shares.

The big surprise was a brand new, $1.6 billion stake in UnitedHealth, accumulated entirely during the second quarter.