Are we really all that different?
Yes and no. It depends what qualities you are measuring. As a general rule I'd agree. If we were very different from each other, or if we merely assumed we were very different, we wouldn’t seriously entertain the question. i.e. I can’t personally see significant similarities between myself and rocks (unless I digress radically from a direct comparison) but I can see certain shared similarities between myself and other sentient creatures which others do not see or will not take seriously.
However...We tend to filter out common similarities so that we can focus on crucial shifts in our environments and it’s also the case that we use perceived differences to bolster our egos and provide ourselves with dubious reasons for justifying our nonessential desires/preferences. This makes for inequalities and non-trivial differences between ourselves that have massive effects on net wellbeing. It’s often these types of relative differences (and the associated consequences) that are of the most pressing interest to us.
In these times we turn to our minds to make sense of it all, to figure out some reason that makes it all okay and enables us to finally lay our burden down. This fruitless quest drives many to madness, suicide, or self-deception. It's a sad state of affairs, but it's reality. Is this the reason for the subtle pessimism that pervades most of our thoughts (and posts) and saying we're happy despite the circumstances is just an attempt to convince ourselves it's so?
Ah… I’ve been down that road but for now I’m content to say that I’m pessimistic because I see that kind of thing happening in others (as well as the other types of suffering) and because it looks set to continue until the sun fizzles out.
Everything that lives must die. It's beautiful, it really is.
I’m more inclined to say that it is tragic. It's certainly a waste of delicate sentience and the end of life is rarely a departure as graceful as one might hope for.
I hate people for wasting even a single moment of our wonderful gift of life. I hate organized religion for telling us what to believe instead of letting us find it out for ourselves. I hate this capitalistic government that forces us to work meaningless jobs for long hours and little pay, robbing us of our right to truly live as we should. I hate pollution and those who pollute for killing this planet, our mother, who bore us all. I think you see where I'm going here. And most of all I hate myself.
I hate myself for being human, for needing to take, consume, and waste, and not having a choice in the matter. For being weak, and for not being able to fix everything and everyone.
I mostly agree except I’d replace the word “wonderful” with “white elephant.” I don’t really hate myself but I consider my presence on this planet to be superfluous for similar reasons you give in the second quote.