Nota bene: a brief article in the New York Times Science section, "Having Cancer, and Finding a Personality," by Ruth Pennebaker. Her description of post-cancer malaise is right on.
"The last time I visited my oncologist after my treatments were over, I felt lost. The image that kept recurring in my mind was that someone with a gigantic pair of tweezers had picked me up, shaken me and tossed me back down. Now what?"
I had my own rimshot moments during treatment. Satire can be used to divert aggression; in my case, joking was more productive than punching a hole in the wall. During my last radiation appointment, the nurse gave me a going-away present: a videotape titled "Moving Beyond Cancer." I told her I'd really prefer it if she gave Cancer a videotape called "Moving Beyond Elisa."