Why can't the good be left alone?

Why must there always be bad to temper the good?   I hate having my pessimism validated.  You all know the good, here's the shit stack:  Mom has leukemia.  

I cannot even write it without wanting to throw up.  She was admitted to the hospital Monday as she had gone to the doctor to have her lightheadedness, shortness of breath and fatigue analyzed, and her hemoglobin was so low that they admitted her for a transfusion.  She had her marrow biopsied today, so we'll know the type tomorrow, and the DNA typing will be done next week.  She'll come home for two days starting tomorrow afternoon, and then will be in the hospital for a month for chemo.

This is a woman who has eaten a healthier diet than an army of vegan hippies, who takes vitamins of varying degrees of strangeness, who works out, who does everything right, and this still happened.  She is the epicenter of the universe to the grandkids, and they won't be able to see her for four weeks.  There is no shit like cancer shit.