Desperation:

Truth has very few friends and those few are suicides. ~Antonio Porchia, Voces, 1943, translated from Spanish by W.S. Mervin

Have you ever done something you hated for years? Something that bored you to tears? Something that made you think of suicide whenever you drove past the cemetery on your way home on a dismal evening?

And then you felt relief, when you realized you could just quit instead of rising before dark to repeat the same day tomorrow. But you thought how could long could you possibly survive without an income without doing that boring something day after day after day.

It's not happiness that drives most writers. It's desperation and lack of hope.