There are some differences that make a difference. You can be similar to another person in many ways and produce a completely different result. All of these variables are within your control.
Attitude: Number one with a bullet. If there is a governor on the level of success you can achieve, it is your attitude. Someone who is positive, optimistic, and future-oriented beats the cynical, pessimistic, self-disempowered person every time.
Discipline: The willingness to do the work that others are unwilling to do is a huge variable. When someone is willing to do what you are not, they will invariably produce a result that is different from yours.
Acumen: The amount of knowledge and experience you have is different from other people, and there can be ever greater differences across domains. The desire to acquire the knowledge and experience is also a variable.
Effort: The person that puts forth the greater effort is always going to produce a better outcome than the person that does the minimum required of them. You may only need a C to graduate from high school or college, but you don’t produce exceptional results by putting forth the bare minimum effort.
Other-Orientation: The person who is more interested in other people is the person who is more interesting to other people. The person who can engage another person in a conversation about themselves and their needs wins out over the person who spends their limited face-time with a client talking only about themselves.
Resourcefulness: This is the linchpin attribute of successful people. They figure things out, and they aren’t plagued by learned helplessness. The willingness to try to figure something out is always going to produce a better result than abdicating yourself of the responsibility to produce a result.
Determination: There are probably times when it makes sense to give up. But when it comes to the things that you really want or the results you need to produce, persistence is the variable. Grit and intestinal fortitude (and even a pigheadedness) are what allows someone to stay the course until they succeed when others give up.
Focus: Some people major in minor things while others major in what is most important. In an age of ever-increasing distractions, the ability to narrow your focus is going to allow you to produce better results than those who fly from one meaningless triviality to the next.
With so much and so many things outside of your control, it is imperative that you control what you can.