Jeopardy host Alex Trebek is going through a second round of chemo after announcing a setback in his battle with cancer.

“I was doing so well. And my numbers went down to the equivalent of a normal human being who does not have pancreatic cancer. So we were all very optimistic," Trebek said. "And [then] my numbers went sky high, much higher than they were when I was first diagnosed. So, the doctors have decided that I have to undergo chemo again and that's what I'm doing."

The 79-year-old Jeopardy host says cancer is "mysterious in more ways than one" saying that he sometimes endures excruciating back pain and inexplicable emotions.

"I talk to the audience sometimes and I get teary-eyed for no reason whatsoever," Trebek told Good Morning America. "I can't explain it -- I don't even bother trying to explain it anymore."

In the video below, Trebek remains optimistic -- even joking about his mortality.

"One line that I have used with our staff in recent weeks and months is that when I do pass on, one thing they will not say at my funeral is 'Oh he was taken from us too soon.' Hey guys, I'm 79 years old. I've had one hell of a good life."