Not well.
Many if not all of the men turned to drink, others were nervous wrecks unable to function, some went mad.
This fact was reported to Himmler, who was advised that many of the men involved in the Einsatzgruppen killings were “finished for life” as a result of the horrors they were inflicting and witnessing day after day. In addition to which, a culture of binge drinking and drunkenness had developed around the violence, with perpetrators aided by and in some cases rewarded with hard liquor.
It was the psychological consequences of the endless, face-to-face murders of millions that led, in the final analysis, to the implementation of the gas chambers of Auschwitz and elsewhere. Himmler was concerned that his “decent fellows”, as he called his SS killers in a speech before SS leaders in Posen in 1943, were being ruined by the abominable acts in which they were having to participate daily.
As opposed to having to shoot to death weeping mothers and their babies, whose bodies would then fall into the mass graves they had earlier dug for themselves, here, in the death camps, the SS men involved did no more than pour the Zyklon-B, prussic acid crystals into the chamber from above; it was Jews who emptied the chamber and disposed of the corpses thereafter.
Even the Nazis acknowledged that murder has terrible consequences, although, in their case, their concerns were for the killers, rather than the killed.