Douglas gets hurt (or sick) but is too stubborn to show it, take time off, or admit weakness. There's a large part of him that delights in being looked up to and he's afraid the rest of MJN will abandon him once they "realize" he's a washed-up old pilot and he'll really have nothing.

Of course, his friends won't let him get away with that. Especially once his lack of self-care worsens the original injury/illness.