Being an entrepreneur means you embrace ambiguity. You learn to comfortably take days that bring you challenges every now and then. Entrepreneurs face a challenging existence that’s often very isolated, due to the independent, self-starting aspect of being their own bosses. As such, every now and again, entrepreneurs need some inspiration to keep them motivated. 
I recommend you to read a previous article 101 Inspirational Quotes for Entrepreneurs

Below are 20 quotes every entrepreneurs should know and live by especially when having to go out for startup fundraising.

“The best time to plant a tree was 20 years ago. The second best time is now.”

This Chinese proverb reminds entrepreneurs that they should live in the moment and not look with regret at the past.

Donald Trump, The Trump Organization

“I was relentless, even in the face of total lack of encouragement, because much more often than you’d think, sheer persistence is the difference between success and failure.”

Steve Jobs, Apple Inc

“Your time is limited, so don’t waste it living someone else’s life. Don’t be trapped by dogma – which is living with the results of other people’s thinking. Don’t let the noise of other’s opinions drown out your own inner voice. And most important, have the courage to follow your heart and intuition. They somehow already know what you truly want to become. Everything else is secondary.”

Also Read: 70 Best Motivational Business Quotes To Inspire Entrepreneurs

Isadore Sharp, Four Seasons

“Whatever you do, don’t ever use a crutch, and don’t ever think of having an excuse for not having said, ‘Yeah, I did my best.'”

Richard Branson

“My biggest motivation? Just to keep challenging myself. I see life almost like one long University education that I never had — everyday I’m learning something new.”

Donald Trump

“Follow your passion.”  None other than Donald Trump himself is behind this quote. The Donald—who’s also running for president in 2016 as a Republican—understands what it takes to make it in this world. His quote obviously refers to the reality that success is so much easier to attain if you already truly, madly and deeply love that for which you’re striving.

Jim Loehr, "The Power of Full Engagement."

“Expose the muscle to ordinary demand and it won’t grow.”  I apply this to that one particular muscle we call the brain. Stretch the brain. Feed it regularly. Challenge it. And watch it grow.

Oprah Winfrey

“Every time you state what you want or believe, you’re the first to hear it. It’s a message to both you and others about what you think is possible. Don’t put a ceiling on yourself.”

Aristotle Greek philosopher

“There is only one way to avoid criticism: do nothing, say nothing and be nothing.” 

For an entrepreneur, accepting and embracing criticism instead of avoiding it virtually guarantees that he’ll eventually be somebody very important who’s done something very important. Through criticism, you learn both how to develop a thick skin and to be humble.

Chris Gardner, Gardner Rich & Co.

"Find something that you love. something that gets you so excited you can't wait to get out of bed in the morning. Forget about money. Be happy."

Martin Luther King

“Everybody can be great, because anybody can serve. You don’t have to have a college degree to serve. You don’t have make your subject and verb agree to serve. You only need a heart full of grace. A soul generated by love.”

I love this quote because it speaks of a leveling of the playing field. Serve first -- everything else will fall into place. 

Jeff Bezos

“One of the huge mistakes people make is that they try to force an interest on themselves. You don’t choose your passions; your passions choose you.” 

Mark Twain

“Twenty years from now you will be more disappointed by the things that you didn’t do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover.”

Tim Fargo

“If you can’t find any joy in life, perhaps you have a vision problem.”

Sherrilyn Kenyon

“Life isn’t finding shelter in the storm. It’s about learning to dance in the rain.”

Bill Gates

“Your most unhappy customers are your greatest source of learning.”

Charles Kettering

“High achievement always takes place in the framework of high expectation.”

Johann Wolfgang von Goethe

“Whatever you can do, or dream you can, begin it. Boldness has genius, power and magic in it.”  

Martin Luther King, Jr. 

“If you can’t fly then run, if you can’t run then walk, if you can’t walk then crawl, but whatever you do you have to keep moving forward.”

Robert Strauss

“Success is a little like wrestling a gorilla.  You don’t quit when you’re tired, you quit when the gorilla is tired”

Winston Churchill

“Success is walking from failure to failure with no loss of enthusiasm.”

Entrepreneurs are the dare devils who choose a career path with the odds of success very low. But still, I’ve read many examples of entrepreneurs who succeeded in making their dreams come true by their laser focus, patience, persistence and perseverance.