Tragedy could do so much to a man.
Greg is a family man even when they are far from him. one day he lost them. so he poured his grief to his work.

He's snappish to everyone. barely eats or sleeps or goes home.
sherlock has to handcuff him to his car so he won't chase after a criminal they we on to.
John manhandles him out of his office after a faint and feels how much weight he's lost.
Mycroft doing something irritating like visiting his office and using that damn umbrella to tap his hand when he reached for a case file.


Holmes brothers deduction and breaking the "caring is not an advantage" thing

pre-John or post-John is good