In "Doomsday" Yvonne becomes a Cyberman and presumably loses all emotion and sense of personal identity. Yet, she resists their control at the end, and kills her own "kind." How? What makes her so special from the thousands of Cybermen before her? As far as I know, no one else has ever been able to assert control once they've been transformed.
Closing Time is another episode where someone defeats the mind control of the Cybermen. As well as that Cyberwoman in the Torchwood episode Cyberwoman (Season 1 Episode 4). It seems as if there is a strong enough emotion (or the process didn't complete for some reason) the person will get over the Cyber control.