Watching my mentor decline from terminal illness — how do I support him?

I have worked at my institution for about 15 years — I started here as a student and stayed. One of my coworkers took me under his wing back then and became my mentor, and eventually my “work dad.” He taught me most of what I know clinically, pushed me to be better, and played a huge role in where I am today.

He’s been there for me outside of work too. He came to my wedding, and when he saw me, he cried like a father seeing his daughter get married — something he never had himself (he has 5 sons, no daughters). That moment meant more to me than I can put into words, and it’s something I’ll always carry with me.

Over the years, I’ve watched him slowly deteriorate from a terminal illness. He’s old enough to retire, but I don’t think he can afford to, and pride likely plays a role. Some days he can barely get up from his desk, and my coworkers and I quietly pick up the slack because we care about him.

We’ve always bonded over dark humor — it’s how we cope, and it’s how I’ve dealt with my own depression. But watching him decline breaks my heart, and I dread the day he just doesn’t come in anymore.

Is there anything meaningful I can do for him beyond keeping his spirits up and treating him normally? Should I say something heartfelt while I still can, or just be there? I don’t want to look back and feel like I failed him.

Any advice or shared experiences would really help.