Mihaly Csikszentmihalyi has done some interesting research on people who encountered tragic accidents. I cannot remember the exact details but it goes something like this:
the study focused on handicapped people who had just lost their limbs in accidents.
The results of the study showed that in most cases, eight or nine months after the accident, the person would rate himself as no happier and no sadder than he had been, prior to the accident taking place.
In a few cases, the person would rate himself as happier than he had been, prior to the accident taking place.