I do my part by bike commuting, conserving energy, reducing consumption, etc.

But I don't worry about the big picture because I can't change it, and I think at this point it's too late to "fix" the problem anyway.

If humans drive themselves extinct it's not going to happen in my lifetime, and it's really not a big deal in the grand scheme of things. We won't kill everything, and something else will evolve to take our place.