How does cancer change the nature of a person?

I am finishing my first cycle of my next chemotherapy treatment. As my illness has already metastasized, the goal of the treatment is now to simply extend my life as long as it can. This is a brutal reality that too many people still deal with even in this era of advanced medical research and public support. But this first cycle has turned out to be gentler than it often is and my body has responded robustly. There is reason to smile today and my spirits are surprisingly high. But the basic prognosis is still very uncomfortable and I have a lot of work to do to reconcile the two extremes: the happiness that I feel this particular day and the inevitable reality that may emerge much sooner than I ever expected.