every thought

Why does every thought I have need to end in the word cancer?  Why can’t I have one full day without that word?  Why do I have to obsess about it?  I wake up with it in my head and fall asleep with it there too.  Some days it’s impossible to think I’m going to get through this.  I know I wouldn’t be able to get through a single day feeling sane without the support of the people around me.  How do people ever get through something like this alone?