T. Boone Pickens is calling it quits

T. Boone Pickens, the iconic oil and natural gas investor, is getting out of the business he has helped shape since the 1950s.

Pickens, 89, chairman of BP Capital Fund Advisors, announced in a letter that he is shutting the commodity and energy stock hedge funds he runs. He cited poor health and advanced age as the reason.

"It's no secret the past year has not been good to me, from a health perspective or a financial one," he wrote in a letter he posted on LinkedIn on Friday. "Health-wise, I'm still recovering from a series of strokes I suffered late last year, and a major fall over the summer. If you are lucky enough to make it to 89 years of age like I have, those things tend to put life in perspective. It's time to start making new plans and setting new priorities."

Pickens said it's the third time in his career that he's walked away from a job. He said he quit a job as a geologist with Phillips Petroleum in 1953 at 25. He said the bureaucracy of a major oil company was frustrating. He soon started Mesa Petroleum, a company he ran for nearly 40 years until he retired in 1996 at 68.

"In both instances, I had a plan, and my life was much richer as a result," he said. He said he became a billionaire for the first time after that retirement.

Pickens said it is time to get his affairs in order and devote his full attention to recovering his health.

He wrote that during his career he's seen oil go from $10 a barrel up to $147 in 2007, and then back down to $26 during the depths of the Great Recession.

"I'm ecstatic that I've hung on long enough to see it all unfold. I've thrived and profited on the volatility in the energy space," he wrote. But he said that despite the recent rally in energy prices, "for me, personally, trading oil is not as intriguing to me as it once was."