Continue to invest/hold, and avoid selling, maybe this way the price of bitcoin can be as stable. But we cannot rely on this method if only done by ourselves because bitcoin is global. After all it's very contrary to popularity which's owned by bitcoin.
As long theres a transaction to do happen there would always been a volatility on price and i cant imagine that bitcoin is solely having a purpose to be just being hold up,avoid selling. Then doing these things is for what?
Bitcoin wont really become stable just like on traditional fiat currencies but when theres a high adoption where coming to a point that majority of merchants do accept it then we might see some gradual increase which i do really prefer rather than having big high spikes.