Keeping a good attitude will help you weather the storms of entrepreneurship. The daily life and grind of entrepreneurship can be filled with big highs and lows, but staying focused on the end goal and seeing the opportunity in your challenges will take you far.

Here are five quotes that will inspire you to keep your chin up from five successful optimistic entrepreneurs who have been where you are now. They just might inspire you to see the possibilities in risk, failure and every opportunity that lurks around the corner when you're open to it. 

1. "The greatest discovery of all time is that a person can change by merely changing his attitude." -- Oprah Winfrey

When it comes to mega success, there are a select few at the top who you don't need to reference their business to know who they are and what industry they're in. Oprah Winfrey is one of those people. She turned a news career into a talk show and her talk show into an empire. However, the real tipping point for Winfrey was when she started focusing her show on making people's lives better. Whether that was in body, spirit or mind, her empire has expanded to make her the go-to guru and established her as a truly optimitistic entrepreneur.

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2. "Optimism helps us persevere. Life isn't easy. But life is always good." -- John Jacobs, co-founder, "Life Is Good" clothing brand

You know those cute little T-shirts that you see around the mall or in airport gift shops with the stick figure that says, "life is good," or the stick-figure dog that says, "bark less, wag more?" Those are from John Jacobs and his brother Bert's T-shirt startup, Life Is Good, that's transformed into a happy brand embraced around the world. It all started with a lot of elbow grease, selling shirts on the street and college campuses. A good attitude can take you a long way, and who knows, might even make you a success story in business, too.

3. "Don't let what you don't know scare you, because it can become your greatest asset. And if you do things without knowing how they have always been done, you're guaranteed to do them differently." -- Sara Blakely, founder of SPANX

SPANX is a globally recognized brand of hosiery that has set Sara Blakely as the youngest female billionaire (and that's self-made). She talks a lot about the success and optimism that's behind failure and how it fueled her to keep going. When you're feeling stuck in a rut or overwhelmed by what you don't know, remember that the optimistic entrepreneur always looks for the growth and the opportunity in challenges. Don't worry about what you don't know -- it could help you change the game.

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4. "Business opportunities are like buses, there's always another one coming." -- Richard Branson

Like Oprah, Richard Branson is another one of those rock-star entrepreneurs who is known without even needing to mention his vast line of Virgin-branded products (which includes a cell phone service, an airline and space tourism, to name a few). Branson is all about risks and big ideas. Sometimes as an entrepreneur you might think the only opportunity is the one right in front of you, or you may even lament one you passed up. However, as Branson says, there are always opportunities wherever you go. The key for the optimistic entrepreneur is to keep your eyes open and see how regularly they show up.

5. "Don't limit yourself. Many people limit themselves to what they think they can do. You can go as far as your mind lets you. What you believe, remember you can achieve." -- Mary Kay Ash, founder of Mary Kay Cosmetics

Mary Kay started her cosmetics empire to provide women with career opportunities from the ground up after struggling with workplace injustices in the early '60s. Her desire to create options for herself and her family in the business world has led to the well-known cosmetics company. But what might've happened for Ash and her family if she had limited her belief in what's possible in the workplace? The optimistic opportunity works like an alchemist to spin setbacks into golden opportunities that create change.

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