This is a completely baffling post. You seem to be conflating dark matter, dark energy, and entropy. The former two are purely theoretical, and not one of the three will prevent us from becoming a trans-solar species. None of them will prevent us from achieving greatness "last to the end." None of them render our efforts hopeless.

Yes, based on our current understanding, it seems the universe will inevitably end someday. But why is that a failure? Why does success have to be infinite to count for anything? You and everyone you've ever met will die someday, does that mean nothing we do in life has any point? Does knowing that a TV show ends in a series finale prevent you from enjoying it? Is it pointless to eat a meal just because your plate is empty when it's over?

Obviously not. We're here, we're alive, and we'll do great things until we--as individuals, and as a species--finally kick the bucket. If you spend all your time fretting that the road will end someday, all you're doing is ruining for yourself what could've been a wonderful ride.