My suggestion would be drowning himself in military/plot-like activity. Spartans, for instance, tend to numb or otherwise ignore their pains and losses by keeping themselves busy in any other way: Missions, exercise, research, etc. Because otherwise, the moment they start thinking about it, the moment they get sad. And even then, they still get nightmares.

In blood knights and people not as affected by combat, it seems to be a bit of a common trope, as with fictional military characters. Sam Fisher of Splinter Cell, for instance, with the loss of her daughter, pleaded to be given a mission when Command discharged him because of his evident depression.

It wouldn't precisely close him off, since he'd need peopleto work with, but they'd notice something's not quite right with Leonhardt.