I’m generally a upbeat person. I try to find something positive in each day, even when the only positive I can find is that I’m still breathing.

But every now and then, lung cancer messes with my head. It’s hard to completely eliminate the memory of an October 2011 PET scan image showing a hot spot outside of my chest, my pulmonologist calling after the biopsy to say my lung cancer had metastasized, my oncologist apologetically estimating I had perhaps two years to live. (Granted, he only gave me a prognosis because I pressed him for one. He has since happily recanted.)

I’ve already had two recurrences, both found just weeks after the end of a chemo regimen. I will be in treatment for the rest of my life. My current targeted therapy has eventually failed for everyone who’s taken it. Chemo eventually stops working because the cancer develops resistance to the drug.

Every two months I have another scan to see if the cancer has progressed yet. My cancer is aggressive and smart. When a treatment thwarts its goal of world domination, it mutates and renews its efforts. And the next treatment option may or may not be effective.

Every now and then, these facts overwhelm me, and I cannot stay positive.

Many people who experience near-death report that when they died, they saw a tunnel, walked through it, and emerged into the light before they were brought back to life.

Every now and then, the facts overwhelm me, and I see that tunnel, or at least this end of it. I become acutely aware of what cancer has stolen from me, and how little time I might have left. I start thinking of important tasks I want to finish before I die, of family I will leave behind, of experiences I will never have again.

I call it “End of the Tunnel Blues.”

When it hits, I usually brave it in silence. Few people want to dwell on my possible impending demise. Some are gobsmacked and uncertain how to feel or respond. Others feel compelled to make me feel better. It seems the only people comfortable talking about such things are those who have seen their own tunnel. Other incurable cancer patients like my friend Jay Lake know.

The feeling usually leaves after an hour or two, but each episode leaves a mark on my soul.

If you have a friend facing a life-threatening or incurable illness, they may have periods of the End of the Tunnel Blues. If they mention it to you, try not to freak out. It’s normal. Just listen and, if you can, let them know you’re honored they trust you enough to share their deepest feelings with you.