The key to winning is knowing when (and what) to quit. No one who has ever achieved greatness in anything has ever done so by trying to master everything that comes their way.
Dozens of studies have documented actual ROI in key performance indicators for organizations that encourage managers to intentionally provide opportunities for people to do what they do best.
You probably have a not-so-favorite story about someone who was such a great employee that they were promoted to manager – and fell to pieces. It happens far too often, doesn't it?