Why do you continue with your shitty attitude?

Attitude is everything. Either you think the universe is unfolding as it should or you think that there is this perpetual injustice, designed by external forces motivated only to fuck you over.
If you think the world, and specifically your world, is shit, why do you keep confronting it with your defeatist attitude?
I am confused by this tendency, not so much generally, but certainly on this site, to believe that existence, life, humanity etc are simply versions of dog shit.
I do not get it.
But one thing is for sure. If you think life is shit, your life will certainly be shit. Why would you want your life to be shit.
So why are you your own worst enemy by imagining that life is shit.
And if you believe it, why not end it?