i guess bitcoin cannot sustain forever, that's why bitcoin is open source and the rise of alt coins. bitcoin can end the control of economy by one. bitcoin is a waste of energy because bitcoin needs mining to maintain its network.
Can you please tell me only one field where we never use our mind and energy? Now time is very fast going, and you should go with it, if you never go with the time than you never found a bright future. So do work like robot then you will successful in your life. Also You know Bitcoin is a easiest way of earning.
Bitcoin is never a waste of energy because of mining. Altcoins aren't going to be able to overthrow bitcoins because most altcoins are only pump and dump schemes and that's just about it. Bitcoin is the only crypto that has the best usability.