The universe around us has 3 parts of reality - a triangular reality - the observer, the observed and the act of observation.
The observer has the power to witness and that is the center of all awareness, knowledge and experience. If the "I" is not there nothing else matters - i.e. matter does not matter unless there is somebody to experience it. And that force that experiences is the center of existence, you may call it "Will". The word "Will" implies in it intrinsically the act of happening already i.e. I will do this, I will be happy etc.
The "Will" indicates a certainty of purpose and it comes from within each of us. It transcends all boundaries and exists in a universal "I-ness" that it is utterly complete. So strength, knowledge are like zeros without a "1" in front of them. That is what is the value of 00 without a "1" in front of them. Answer is nothing! But if you do put a "1" (signifying will) in front of the zeros it becomes 100 or total/complete. A successful person therefore is one who realizes this "1" in them and puts it literally first before all the other things. And that is indeed the key to success.
The difference between a successful person and others is not a lack of strength, not a lack of knowledge, but rather a lack of will. This is very true quote that puts the will of a person as the most important thing to conquer you goals.
You don't need to be very intelligent or rich person because if you have the will and work towards that goal, you are demonstrating to yourself that you are capable of achieving all that a successful person would. This will obviously imply a lot of effort, because the thing we want just won't fall from sky. The person would have to work hard, focusing all energies and thoughts to walk through that hazardous path and get to the other end.
You can be rich and even intelligent but if you are not willing to put in some effort and rely on other to get what you wants, you are going in the wrong direction.
A person, who knows what he wants and fights against everybody and everything to prove the truth of his ideas, is a true person. He is a person who gives up laziness and puts on the working pants. Everything in this world involves effort and will, so that is what is takes to be successful person.