Meaning is hijacked early on in life. You enter a mythical forest around age two, reeling as your pre-verbal infancy narrative falls apart, swarmed by comforting tales of mommy love or being cradled in the bigger, safer arms of God or society, and the path you're on goes to heaven or at least human betterment, you're told. You're going somewhere, to a better place and all sorts of horrors come to play a valuable role. The bad becomes good.
But the forest is a tightly bound ecosystem so when the first tree catches fire, the rest eventually burns down with it. You try to partition but can't. What you're left with is a charred, meaningless wasteland. Now you're watching the people you love talking to phantom trees.
What killed the forest doesn't discriminate between bad and good. What killed the forest evolved to destroy, not create. But it became who you are.
And yet, while you know the old meaning is dead, you know it's also not true that life is meaningless. Every action, every day, you are giving quite a shit. Despair is an extreme form of caring. Your life just doesn't have that meaning anymore, the one that had kept you cowering. Nihilism (I'm thinking Bright Eyes' "Waste of Paint") is an addiction to suffering, a failure to let go, a commitment to feeding the fire long after it's done its job.