One article that I found was Spinal Cord, (21 June 2011), "Predicting the long-term impact of acquired severe injuries on functional health status: the role of optimism, emotional distress and pain," by O Vassend, A J Quale, O Røise, and A-K Schanke.
(I found this by searching Google Scholar for "patient attitude spinal cord injury," which led me to several articles on the journal Spinal Cord. There seemed to be quite a few articles dealing with medical staff attitude, so I just searched Spinal Cord archives for "patient psychology.")
The study used a hierarchical regression analysis and a sample size of n=101, with a follow-up 4 years later with n=75.
It doesn't say whether patients who adopt an optimistic attitude do better, but instead, that patients who have an optimistic attitude fare better. The article concludes: "high optimism should be regarded as a resilience characteristic, protecting the individual against long-term sequelae of severe physical injury." In contrast, "patients characterized by low optimism, combined with presence of pain and depression/anxiety, may constitute a high-risk group for disability and reduced quality of life."
So there may be something to be said for going in with a "can do" attitude.