Why do I feel guilty?
People feel guilty for burdening their family, for missing work, for not being cheerful enough, and for having caused it somehow. All of it is common and none of it is deserved.
Your family would almost certainly rather carry this with you than have you protect them from it. If guilt is stopping you asking for help, that is the thing to say out loud.
Written by two physicians. Checked against patient information from the US National Cancer Institute and Cancer Research UK.