Q:

Alternative for ‘gute Besserung’?

Can gute Besserung be said for someone who’s fighting cancer? Or is it just for illnesses that are not life-threatening such as flu?
Does an acceptable alternative to gute Besserung exist for life-threatening illnesses?

A:

In the sense of »Halt die Ohren steif!« you could say

Lass dich nicht kleinkriegen!

or

Lass dich nicht unterkriegen!

meaning »don't lose heart«.

