I wanted to add that I strongly agree with Brian's thought that one thing my positive attitude did make a difference with was that I tolerated pain and discomfort without as much complaint as someone with a less optimistic attitude. This has been true for me in other medical situations I've been in too, before the cancer. In the last 5 years, there have been about 4 separate occassions when a doctor (different one each time) has said to me "I'm really surprised you aren't in more pain" and I've always thought that what the doctor really meant was "I'm really surpised you aren't complaining more about the pain you're in" because I WAS in pain at each of those times. But I have practiced mindfulness meditation on and off for about 7 years and I think that creates a different response to pain and discomfort sometimes (sometimes. I won't say that I've never been just crazy with pain because I have).

But I don't think that optimism, or any other psychological variable I had going for me, really meant I experienced less discomfort, I just reacted to it differently.