the arrow like nature of time is, right now, to the best of our knowledge, there.
Another of my mentors has died. Someone with whom I had, at best, a prickly relationship. Someone from whom I learned a lot. I did say thank you, a couple of years ago, in an article that I sent him about the field he helped define.
There is very little in my life I regret. Lots of stuff I did wrong, lots of stuff done wrong to me. But little to regret. Say thank you to those that matter. One less thing to worry about when they die. As they will.