BlackRock CIO Rick Rieder has faced criticism from Morgan Stanley's "Hard Lessons" series about his worst bets, including a Peloton position that collapsed, a hedge fund launched months before the 2008 crisis, and bond trades that nearly derailed everything. His admission was a direct lesson for investors about how to manage risk in their own portfolio. The lessons include that strong products alone cannot sustain share price appreciation, and that leadership can execute fundamental pivots when the original thesis breaks apart. A bond trade that nearly ended everything nearly ended Riedher's career also taught him that one security, if sized incorrectly, can threaten an entire career.