I think that we are alive for one purpose. We can't live our life's by ourself. The life is a soil, we're gardeners and our actions make one seed growing and turning in a flower. All action, have one re-action. We need to let something in this world, something good, making the world better.
For me, the key to success is "to believe". And there are many people that made some difference in my life.
First of all, I consider the first priority for us to discuss this topic is to ensure the definition of success then we can expect to stand on the same line to explore. I speculate there are a bunch of definitions about SUCCESS in the world and there is no universal standard to measure what the real success is but yourself.
Accordingly, I would like to define success on my own which is "self actualization, fulfillment". In this case, only I self can define my success and I consider the key to success is "flexibility", nothing more.
Thanks for your question to remind to think as I am here.
Persistence and the ability to deal with "failure"/setbacks. I can think of many people who I would consider mentors but I seem to be much more motivated by someone telling me I can't do something than people who are supportive.
"Failure is either giving up or being content too soon."
It´s nice to see this kind of thinking, because we all have to be believers, it´s important to have goals no matter if they are extremely difficult because if you really want to achieve something you will work hard to achieve it. In my opinion every single person has goals and dreams but the problem is that they lost focus, there are several things that make us lost focus for example bad or negative friends, the society in general... But if you never lost focus is probably that you can achieve what you want, and if you don´t achieve it you will learn a lot in the journey and maybe in the journey you create others goals and dreams and it continues until we die. That the beautiful thing in people and because of dreams and goals is that humanity has accomplished all things like technology and science, because those "genius people" made mistakes too but they didn´t give up and now it our turn to change this world action by action.
For example: learn other languages make us take big steps because if we can communicate with people of other countries we can share knowledge and experiences and that make us smarter.