Some define it as having a lot of money.
Some feel that it happiness of the family.
It can also be, having good degrees in education.
That's fair enough to say that it is ones own satisfaction level. If you feel that you would be happy when you have reached your goal you are successful. But we are never satisfied with the success we achieved. We try for the better. Thats why it is said that "Success is not a Destination but a Journey"