The Leadership Insider network is an online community where the most thoughtful and influential people in business contribute answers to timely questions about careers and leadership. Today’s answer to the question “What’s the most important lesson you’ve learned in your career?is by Andrew Laffoon, CEO and co-founder of Mixbook.

In the summer of 2008, the future looked bleak for Mixbook. Although our usage numbers were exploding with millions of new users, our revenue numbers were not keeping up. My co-founder, Aryk, and I visited over 50 different venture capital firms to ask for money, but we left each one empty-handed. After four months of asking anybody and everybody for funding, we finally got a term sheet for an angel round led by the Band of Angels. We decided to proceed and negotiated the term sheet, adding more investors to the round. We were on track to close $800k in funding, more than enough to enable Mixbook to continue for years on our incredibly small burn rate.

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We were so confident in the round we were closing that when another investor came in to compete with the lead on our angel round, we declined to entertain competition. Just two days later, our funding round fell apart. We were left with just weeks of cash in the bank, and it seemed highly unlikely we would find additional funding in the short time we had. Shockingly, we found out that the other investor we declined had called our current investors and convinced them not to invest in us. As soon as we found out, we called the original investors and put the round back together within 24 hours, with time to spare before our cash crunch.

At Mixbook, we’ve certainly had a roller coaster of experiences along the way to building a sustainable business. From nearly running out of cash to lawsuits to former employees trying to extort us to layoffs, all issues sadly too common for rapidly growing companies. However, despite all the downfalls, I learned one of the most important lessons in my career: success comes to those who persevere despite the odds and never give up. As an entrepreneur, you have to have the grit and determination to face seemingly immovable obstacles and impossible challenges, to bear the crazy ups and downs inevitable in startup life, and look for solutions instead of obsessively worrying about the problems. If you have a big goal in mind –whether it’s a startup, a lofty career ambition, a non-profit or a personal project — don’t give up. Take steps everyday toward your goal, and don’t let anyone tell you ‘no’.