It's not intelligence or education that predicts success. Instead, it's something far less tangible and much harder to measure: grit. So says psychologist and MacArthur Fellow Angela Lee Duckworth. In a 2013 TED Talk Duckworth revealed this finding from she'd learned after years of studying what it takes for people to succeed. 

What is grit? Duckworth says that "Grit is passion and perseverance for very long-term goals. Grit is having stamina. Grit is sticking with your future, day in, day out, not just for the week, not just for the month, but for years, and working really hard to make that future a reality. Grit is living life like it's a marathon, not a sprint."

I can certainly testify from years of helping people achieve their success that resilience and inner strength are qualities I see in those who make it. Grit, in a word, is that intangible quality that you need to succeed as a leader and entrepreneur.

How can you develop or strengthen the grit that you need to be a success? Begin here.

Develop a growth mindset.

Stanford University psychologist Carol Dweck introduced the concept of a "growth mindset." People with a growth mindset believe that they can better themselves, their abilities, and their minds. They endeavor to learn new things and to develop new skills. "This view," Dweck explains, "creates a love of learning and a resilience that is essential for great accomplishment. Virtually all great people have had these qualities."

Dweck's research demonstrated that fostering a growth mindset encourages people to be, well, grittier. People with a growth mindset are more resilient and motivated to succeed than others. They treat their brains as muscles. Remember, muscles can get stronger as they work to learn more and better themselves.

For entrepreneurs and leaders, developing a growth mindset is crucial. If you want to lead your business to success, you need to operate on the assumption that you can always be doing something better. That's how you'll excel in your field, gain client loyalty, and develop innovative ideas. What's more, a growth mindset will help you feel motivated to pull through the inevitable moments of failure.

Practice Mindfulness.

One of the ways you can develop grit and a growth mindset is by practicing mindfulness. Practices like meditation can reduce stress, make you more self-aware, and enable you to better develop a growth mindset.

By helping you manage stress, practicing mindfulness can also help you become consistent in your work and your habits. You'll be better equipped to work incrementally towards your goals, bit by bit, every day. 

Treat Failure as a Learning Experience.

The ultimate sign of grit is the ability to deal well with failure. A person with grit won't be destroyed when things go wrong. They'll learn from failure, and then they'll keep working on toward their goals. This is a key quality of successful leaders--and one that you can develop if you remember that failure is just a step on the road to success.