I am a pup years wise in comparison to you, but can say that you are correct that you must never give up, when faced with something like cancer.
I am about to turn 56 and retire. But at age 48 I was diagnosed with a rare (benign) tumor of the head (skull base). Very difficult to operate on, with low success using a gamma knife, and a frightening level of morbidity during surgery (14 hrs in my case). At the time I was in excellent physical shape, so having a cold that would not seem to go away, I went into see the doctor only to be told (after several tests, CAT scans and MRIs) that I had a tumor the size of a golf ball located at the base of my skull, that was slowly cutting off blood to my brain (was wrapped around my carotid). The news was...well, a shock. The surgery(ies) were...brutal. Lost hearing, had paralysis on the right side. Recovery was...brutal.
But as you said, you just have resign yourself to never giving up. I coded after my 3rd surgery...while conscious. Passing over to the other side is quite easy and comfortable. Coming back though, that required that same "never give up" attitude, as I realized I wasn't breathing anymore, and needing to force that to happen. It was hard. But after keeping at it (focusing on trying to breathe) I woke up to the Neuro ICU staff standing over me with a defibrillator.
There is no doubt in my mind that had I just given up, I would not have come through it all. So your advice is spot on. Never. Give. Up.
I am now back to almost a full recovery (which will never happen), but can still do most things I enjoy, even if not at a competitive level anymore. But the recovery was, as you say, successful from making the decision to not give up.
Much respect to you Merlyn. I only hope we all can have that same attitude in our advanced years.