I highly agree with Heraclitus in that in the world the only thing that is constant is change. I however, don't feel that this is a pessimistic view of the world. I know that everyday my children change, even if it is just in a small way, not always in a good way, but there is something different about them. How can experiences not change who you are or who you become? If his counterpart Parmenides was correct then nothing would change, no one would grow or create as human beings, life would be very boring. Not saying that change is always a good thing, but the lack of change causes stagnation.