The first and oldest reason I stay sane is that I am an author, and above tropes.
Nobody is above tropes. Tropes are just patterns you see in narratives. Everything you can describe is a trope. To say you are above tropes means you don’t live and exist.
Going mad in the face of the oncoming end of the world is a trope.
Not going mad as the world ends is also a trope, you fuck!
This sense -- which I might call, genre-savviness about the genre of real life -- is historically where I began; it is where I began, somewhere around age nine, to choose not to become the boringly obvious dramatic version of Eliezer Yudkowsky that a cliche author would instantly pattern-complete about a literary character facing my experiences.
We now have a canon mental age for Yud of drumroll nine.
Just decide to be sane
That isn’t how it works, idiot. You can’t “decide to be sane”, that’s like having a private language.
Anyway, just to make the subtext of my other comments into text. Acting like you are a character in a story is a dissociative delusion and counter to reality. It is definitively not sane. Insane, if you will.