This post is part of a series in which LinkedIn Influencers share how they turned setbacks into success. Read all their stories here.

I once read that four of the main triggers of depression are losing your job, moving out of your home, divorce, and the death of a family member or close friend. In 1996, I was four for four.

I had lost Mesa, the company I had founded and led through four decades. My 24-year marriage was ending in a nasty divorce, and I had moved out of my house into a hotel. My best friends, Jerry and Jane Walsh, had died in a car wreck. And my dog Winston seemed to have forgotten who I was.

I had spent most of my life winning. Now I was taking some hard hits. Would it surprise you to learn that I was eventually diagnosed with clinical depression?

At 68, I was well past the official age of retirement, and certainly at a point when most people would be happy to call it quits. Not me. I was still Mesa’s largest shareholder, and I had a clear goal for my new company, BP Capital: to become a leading commodities fund.

Throughout my career, I’ve been known for my optimism and a confidence that any obstacle or failure could be overcome. Now everything seemed to be going downhill. The company wasn’t doing well. I wasn’t doing well.

Entrepreneurs tend to develop a sense of infallibility, but all too often they neglect their personal lives and their mental health. They don’t allow themselves time to relax or recharge. They don’t work out or watch what they eat. Physical and mental health problems will bring you down just as easily as other factors. I clearly had let something slip. I had ratcheted down into depression and never realized what was happening. Now I had hit bottom.

A psychiatrist put me on antidepressants. It turned out to be a quick fix. Everything started clearing up. The things I felt I couldn’t change began to change. I felt better, exercised more, and was soon back to being Boone again. I began emerging from a really dark decade. Everything was starting to fall into place. I realize it’s not that easy for everybody, but I was fortunate. Looking back on my past, things began to make sense. It wasn’t the world against Boone. It was Boone against Boone.

Once I put the past behind me, my mind cleared, my focus returned, and I was on my way. Things will get better if you hang in there and believe in yourself. The attributes and skills that made you successful in the first place don’t disappear. I had been struggling at the plate for five years or so, but I was entering a period when nearly every swing would result in the ball going out of the park.

A good hitter learns to hit a curveball. It just takes more concentration. As always, success hinged on the price of oil and gas. After a decade of being too early, my theories were finally about to be proven right. But it wasn’t enough to merely be ready for the challenge mentally. I had to also be prepared physically. When you’re young, fitness is sport. As you grow older, it’s a necessity. Believe me – I know.

This combination of mental and physical fitness – coupled with the biggest rise in the history of natural gas – led one industry observer to describe the next chapter in my life toFortune as “one of the great individual trading runs of all time.”

I was sure glad to finally turn the page.