to develop a way of dealing with a sad situation so that it no longer upsets you

You see all sorts of terrible things when you're a nurse so you become hardened to it. 当护士时见过各种可怕的事，于是你就对这些习以为常了。

After so many scandals, the public has become hardened to this sort of misbehaviour.

Even teh village's children have become hardened to the violence of the war.

She was as hardened to the suffering of others as she was to her own.

I couldn't ever be a veterinarian - I'd never be able to become hardened to seeing animals in pain.