The third law of physics stablishes that a force applied to an object generates an equal and opposite reaction. It's so funny to hear that. So many times we apply energy into stuff and get no apparent reaction at all, that's entropy.
Entropy is the differential of energy that's absorved from chaos, in a manner of speaking —I don't wanna get technichal. Being the case that energy never comes back to the universe, it's dismissed. Some people (smart ones) say that eventually we are going to run out of energy due to entropy, that day the world is going to end.
How epic is that? every single effort we seem to waste, that we seem to see fade into a void, only contributes to a greater purpose... "the destruction of the universe".
Yeap, like that. Every match we burn can't burn to its ultimate potential, every love letter we write with no obvious feedback gets us closer to the end of the universe. So if at any bitter and sour point you feel like you've wasted your time, well, in that sadistic moment take comfort that you've destroyed part of this universe.