That ability to ride the ups and downs is one of the few things you actually control in building your company. It can also be your greatest competitive advantage, as the faster you’re able to bounce back from a setback, the faster you’ll be able to move forward.

You develop mental toughness and resilience just like you develop a physical muscle, by applying stress so it becomes stronger. The good news is that every day of building a company offers plenty of opportunity to train and get better.

Even if you weren’t born an effervescent optimist, you can train yourself to bounce back quicker and stronger. Here’s how:

Hit fast forward to acceptance.

When you’re focused on a certain outcome — landing a major client, say, that will validate you in the market and generate much-needed revenues – it’s painful when it doesn’t happen. Wishing for a different outcome, however, creates resistance that only slows you down and keeps you from taking positive action. You don’t have to like what happened, just accept that it did.

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Reframe the situation.

Still, when things aren’t going your way, it’s normal to be discouraged and wish it weren’t so hard. This is where mental toughness — the ability to persevere in the face of adversity — comes in. Entrepreneurs who perform well under pressure learn to put a different spin on challenging situations. They see obstacles and think: “Here’s a chance to prove myself.”

Shift to solution mode.

As humans, we’re wired to focus on problems. But, as retired Navy SEAL Brent Gleeson told me, if our largest client cancels “and I run around the office with my hair on fire screaming at everybody because we just lost our most profitable client and we’re going to be negative for the next quarter, what kind of message does that send to the team?”

To be successful as an entrepreneur, you have to override the natural tendency to focus on the problem and train yourself to quickly shift your focus to how to solve it. “If you control your emotions, stay calm and step back and assess the true reality of the situation and start developing some possible solutions to it,” says Gleeson, “then you’re going to be able to make good decisions in a chaotic environment.”

Dan Kan, who recently sold his company Cruise Automation to GM (GM) for $1 billion, says: “The way that I approach it is that every problem, or every situation that can give you stress, is just another problem that you have to solve. So if you can think about it rationally, step back and say, ‘OK, what can I do to make this work?’ That is how we approach everything at Cruise and how I approach everything in my life.”

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“Stepping back” is a piece of advice you can take literally. It gets you out of your head and makes the shift to solution mode more concrete. In fact, you can adopt “The 10-step rule” from golfer Tiger Woods’ playbook. When he misses a shot, he allows himself to feel bad about it for the time it takes to walk 10 steps. After 10 paces, he shuts the door mentally on the negative thoughts and focuses on moving forward. It may sound easier said than done — 10 paces isn’t all that long to rebound from most problems — but the idea is to avoid dwelling on your setbacks without thinking about how to move on.

Now that you’re in solution mode, ask yourself: “What’s one thing I can do now?” After losing three big clients in three days, Niall Harbison, founder of PR firm Simply Zesty at the time, sent 30 handwritten letters to his existing clients, updating them on the company and thanking them for their business. They didn’t lose another client for a year.