I'm currently re-watching TOS, and it's fun seeing the wild swings in behavior on this topic from one episode to the very next.
In "Friday's Child", Kirk lambasts McCoy (pretty unfairly) for the loss of a random redshirt at the start of the episode. McCoy: "Look Jim, I know what it means to you to lose a crewman."
In the next episode, "The Deadly Years", poor, young Lt. Galway dies horrifically of accelerated aging right in Kirk's arms. We saw how terrified she was of her condition through several lines she got earlier in the episode. Practically nothing is said, and by the end of the episode Kirk is a grand mood, joking, and making the moves on hot-lady-of-the-week Dr. Janet Wallace.