Rule #1 of Horror writing is ADD SOME FUCKING HUMOR! If your story is doom and gloom all the time, it stops being scary and dark and becomes insufferable and boring.
A tale that is perpetually dark in tone becomes tiresome very quickly. It needs to feature the occasional ray of light for contrast and to create a sense of hope. Monsters and other terrors must be offset with creatures that are kind and lovable, giving the characters even more reasons to stand against the darkness. Here are a couple of ways to add glimmers of light to a tragic tale:
In a land as dreary as Barovia, take the time to describe the occasional scene of beauty, such as a pretty flower growing atop a grave.
Make sure that the heroes have contact with NPCs who are honest, friendly, and helpful, such as the Martikovs in Vallaki or the Krezkovs in Krezk.
-Curse of Strahd, Introduction. Marks of Horror. 2016.
I am currently running it and I am absolutely not sure how to get everything neatly together. It is an absolutely great campaign but here and there (at least to me) it gets quite hard to run.