Dream from last night:
I was in some weird super-post-apocalyptic world. I was an old woman floating as though a ghost would through this cage, remembering the world that was there before, and the events that lead to this position.
There was a great threat to the earth, and the humans were all but destroyed when they discovered a hero amongst the last straggling few herds of beings before their final demise–presumably before I became a wondering ghost of a woman. This hero, however, could not defeat the enemy presence in this time, because they had become to powerful–instead, we sent him back in time to eliminate the threat before it became one.
And he did. The hero cleanly destroyed the enemy. In fact, no other adversary to humanity existed thereafter, and all humans became lush, happy, peaceful people. So peaceful, in fact, that all forms of destroying life were outlawed–to such an extent, in fact, that they went back in time and killed off the hero before he killed off the enemy-threat.
Then, the future from which the dream began became the reality. The futility of time travel. The vein try to change the past–because the present is exactly as it is.