The fallen angel Lucifer's name literally translates to "light bearer". He is cursed, banished from God's realm, never to set foot on Heaven's Gates again. If he's the bearer of God's first creation, why banish him?
In Greek Mythology, the titan Prometheus gave humans the gift of fire. After that, he was bound to a rock by Zeus and let his liver be feasted upon by a bird of prey everyday for eternity.
Why curse them? Had they done anything wrong? They brought light to humans; light which is very essential to human living. If they did anything, humans enjoyed it and lived with it for a long time to the present time. What's the big deal?
Without light, humans and most creatures are rendered helpless. But the light stated here may not be light in its literal sense. Light means knowledge, hence "enlightenment". Even in its altered sense, this light is still essential to human living.
Lucifer and Prometheus defied the one in charge of the world, God (or Zeus). They brought to humans the light of knowledge. Lucifer, tempted the humans to eat from the tree so they can attain enlightenment. Why is it bad?
I can say this for sure though: If god does exist, he has no power over us. He is absolutely not omnipotent. Same with Lucifer. Humans have the power to choose between Knowledge and Ignorance. That is free will. If we would be grateful to some spiritual entity, we should thank Lucifer for giving us the gift of Light.
Upon choosing the Curse of Light, we, as enlightened ones, shall suffer. Suffer what? Suffer the responsibility of this wisdom. Knowledge is Power. With power comes responsibility.
Spiritual entities aside, it is our choice if we head back into the Bliss of Darkness or the Light of Knowledge. As with all dualities and mediocrities, we should all head to the middle, where we can savor the pursuit of knowledge while leading a blissful life.