person A: I am sad that I didn't drive my mother to the airport
person B: Why? Was it because you didn't take those last few moments to spend time with her? Sometimes we have so much going on_comma_ we don't have time to do it all!
person A: I had an emergency at work. I am a doctor and it was a life and death situation :( but now I regret because I could have assigned someone else and driven my mother because that was her life visit 
person B: Oh_comma_ no_comma_ I'm sorry to hear that. You had no idea that would be the last visit_comma_ but I can understand how you would feel that way. I have no doubt she understood why you didn't though.