I think that's a false dilemma. In my mind, part of "fighting" cancer is trying to mitigate its impact on your everyday life, and acceptance probably plays a key role in that process. It's not like being angry and afraid makes you any better at fighting a disease. If anything "fighting" and "accepting" could be said to go hand-in-hand, especially with respect to illness.

in fact, constant stress would make body even weaker. psychosomatism is a real thingie. not that happy people cannot die from cancer