The second perequisite is a creative streak. I think all artists must have a yearning for immortality, that is, a wish that what they have to say in paint (or whatever medium) will live on after them and be treasured, enjoyed, and understood by posterity. That speaks of a strong ego. It also speaks of a strong intellect. But uncreative art seldom survives, and like the artist who has difficulty drawing, if the creative effort is too great, then it becomes too time consuming and thus too "dear" to the artist to part with.
And the third prerequsite is a strong work ethic. Art attracts lazy people. I've seen it dozens of times. Art can be fun, can bring pleasure, can bestow a great deal of joy upon the artist, but it IS, afterall, artWORK. The artist that doesn't work doesn't gain experience, doesn't get appreciably better at his or her art, and also doesn't produce a sufficient quantity of work. Thus, what he or she does produce is too "dear" for the artist to part with.
What we have, then, is a sort of tripod. Theoretically, the most successful artists are those with three equally strong, (or long) legs upon which to build a career. Unfortunately, I've never met an artist yet whoes "legs" are all the same length. Each of us have more length in one or two of these "legs" and are inevitably weaker in the other. That's what makes us all so different, and what breeds differing degrees, and definitions of success.