HOWARD MARKS: These 16 pieces of time-honored investment wisdom have problems

"It's not supposed to be easy," Berkshire Hathaway's Charlie Munger says about investing. "Anyone who finds it easy is stupid."

Oaktree Capital's Howard Marks couldn't agree more.

In his new 15-page memo titled "It's Not Easy," Marks unpacks Munger's conclusion.

In his discussion, he considers 16 pieces of market wisdom and rules of thumb that often get thrown around. And he breaks down just how wrong they are.

"It's a collection of time-honored bromides that range from (a) only effective part of the time to (b) just plain wrong," Marks wrote. "These investment myths are pervasive but of little help. That fact leaves the investor to struggle in a complex, challenging environment."

We've compiled the 16 rules and Marks' critique of each below.