Well, the human species (experiment, as you call it; who is the experimenter?) will eventually disappear one day. 99% of the species that have ever lived are now extinct; why should we be any different?
The second most successful organisms on this planet, the dinosaurs, existed for an incredible 185 million years (making our existence a mere blip so far) but were eventually wiped out virtually overnight. (The most successful are, of course, bacteria, without which no animal or plant life could exist and which themselves can survive in all manner of extreme conditions.)
It sounds unlikely that the present problems we have, when balanced by all those wonderful, magical, positive, optimistic factors which you, in your pessimism, choose to ignore, will be enough to decide our fate. An asteroid is more likely.
Why not enjoy your life while you have it? You'll never see a sunset or baby's smile, hear a beautiful piece of music or read fine words after you're dead. Isn't this life, even through your gloomy glasses, better than the black oblivion of the grave?