This looks like a reflection on a troubled and unsatisfying life to me - maybe a midlife crisis. The three pretenders represent the author's perception of who he was at different points in his life, and kind of resemble Dickens' Christmas ghosts. But perhaps they aren't accurate representations, hence "pretenders." They seem to be distorted memories conjured up by his insecurities.
This looks like a reflection on a troubled and unsatisfying life to me - maybe a midlife crisis. The three pretenders represent the author's perception of who he was at different points in his life, and kind of resemble Dickens' Christmas ghosts. But perhaps they aren't accurate representations, hence "pretenders." They seem to be distorted memories conjured up by his insecurities.