Humanity is living in an (almost) endless painful cycle of civilisations rising, prospering and falling, like a phoenix rising from its ashes, only to burn again. No civilisation, nation, or idea can escape. Some might be able to avoid destruction for longer than others, but they will eventually meet their end.

Death is and should be inevitable, and it's a good thing. I have gotten over the fear of dying when I was eight, yet so many people, (way too many of them are adults) seem to treat death as a sensitive and even taboo topic.
I find the thought that I'll most likely be able to rest peacefully either in a state of non-existence or some sort of afterlife to be calming. I tend to think that the acknowledgment of our own mortality is the only thing that makes us truly enjoy life, as we know it won't last forever. This is the reason why people talking about technology that could make immortal people without thinking about the downsides enough really concerns me. Humans are supposed to be born, to live and to die.

If we want to define whether an action is immoral or moral, then as a rule of thumb, it is moral as long as it doesn't hurt anyone. (yes, this includes non-human animals) There are a lot of exceptions of course.

Humans are not superior to other animals. The reason I think that, in general, killing another human is worse than killing another animal is not that human lives matter more than lives of other animals, but instead that you shouldn't kill your own species.