Yelena Nikolayevna Baturina (born 8 March 1963) is a Russian Billionaire businesswoman and philanthropist, based in London, and was married
to Yury Luzhkov, mayor of Moscow (from 1992 to 2010) until he died in 2019. She founded Inteco (1991), an investment and construction company and for two decades served as president. She is also the founder of the Be Open foundation.
“I demand a lot from myself and reflect this attitude upon others: I consider it to be an important quality for a leader. I also think it is impossible to achieve success without persistence.”
Most people who are wildly successful seem to demand a lot from themselves. I personally have seen many people, including my father, demand and push themselves to the edge. Seeing my father deal with heart disease 
(which eventually took his life) due to his lifestyle, I am not sure if demanding so much from yourself is a good thing.
On the other hand, persistence is another story. Being politely persistent is a good trait to have and practice. Several people, over the years, have told me how much they appreciated my persistence. Why? Because I was always in the forefront of their mind because I was persistent. And this made the sale for me, in many cases.
So, I wholeheartedly agree that it is nearly impossible to achieve success without persistence. Next time you want to quit, hang in there a moment longer to see what happens!