People can choose appreciation as a practice, in the most dire circumstamstances. In fact, it's even more important to practice appreciation where you can, when things aren't great.
I always practice mindfulness more diligently when I am tired or busy, because being mindful improves life during hardship. Being slow or deliberate, breathing and relaxing on purpose, and focusing on one thing at a time can make each moment better.
Can there be mindfulness and appreciation in a situation as extreme as Palliative Care, or after memories of a Holocaust?
This article from Willem Kuyken for Psychology Today says yes.
...And if you haven't seen Life is Beautiful (La vita è bella) with Roberto Benigni, the possibility of finding beauty amid horror is played out in this Oscar winner. A father protects his son from the nightmare of a Nazi concentration camp by maintaining his infectious humour, and convincing him they're playing a game.