“The Middle Years” Commonplace

“The art had come, but it had come after everything else. At such a rate a first existence was too short–long enough only to collect material; so that to fructify, to use the material, one must have a second age, an extension.”

James, Henry. “The Middle Years.” Henry James: Complete Stories 1892-1898, ed. John Hollander and David Bromwich, The Library of America, 1996, p. 338.

Unclear what “everything else” is referring to. What has happened to delay Dencombe’s artistic success? Why does he not observe this to be a success, as it is clear that even after being setback he was still able to create art in the first place? Why does only one successful artwork not make him a successful artist?