You win some, and you lose some, and even the best investors in the world can pick the wrong investments, including billionaire hedge fund manager Carl Icahn. After Hertz (HTZG.Q) filed for bankruptcy protection a week ago and its stock price plunged to less than $1 per share, Icahn threw in the towel on the vehicle rental company he had amassed a significant 39% chunk of. Over a six-year period of investing in the company at various prices, Icahn had put in roughly $1.88 billion. And when it was all said and done, he sold his more than 55 million Hertz shares for $0.72 cents -- for a total just under $40 million.

In a security filing, Ichan had this to say:

I have been an investor and supporter of Hertz since 2014. Unfortunately because of Covid-19 which has caused an extremely rapid and substantial decrease in travel, Hertz has encountered major financial difficulties and I support the Board in their conclusion to file for bankruptcy protection. Yesterday I sold my equity position at a significant loss, but this does not mean that I don't continue to have faith in the future of Hertz. I believe that based on a plan of reorganization that includes new capital, Hertz will again become a great company. I intend to closely follow the Company's reorganization and I look forward to assessing different opportunities to support Hertz in the future.

Seemingly endless rows of parked vehicles.

Image source: Getty Images.

Hertz will now turn its focus to selling some of its rental vehicles while in bankruptcy to bring its fleet size in line with the declining demand for travel -- a development that could hurt the auto industry further as it would pressure used car prices. Hertz has roughly 60 days left in bankruptcy protection to negotiate with creditors and major lenders of its substantial pile of debt. Hertz's bankruptcy is a reminder that while broader markets will rebound from COVID-19, not all companies have the liquidity to weather the storm. Make sure to do your due diligence before investing, because even the world's best investors can get burned.