First of all, don't give up. Advances are being made in cancer treatment every day. There's always a chance.
My best friend is currently battling cancer. His determination to beat it is an inspiration to me. I'm sure he will win.

As your countryman, Mr. Churchill said:
“Never give in. Never give in. Never, never, never, never—in nothing, great or small, large or petty—never give in, except to convictions of honour and good sense. Never yield to force. Never yield to the apparently overwhelming might of the enemy.”

As for your firearms license, I'm just flabbergasted. Why should your health even matter? Surely there must be some way to fight that as well. Refer to the above quote.