Bitcoin is decentarlized, and if something is decentralized you are going to have a lot of volatility. There is no way that you will be able to change this, until merchants are able to accept bitcoin at face value and not fiat value of bitcoin.
Foreign exchange markets are realtively stable compared to bitcoin because governments are actively manipulating their currency. exporting countries in particular are slowly but steadily trying to depreciate their currency. If a country's national country rises too much, the central bank is able to dump a whole bunch of their newly printed, fresh fiat onto the market, driving the price down. If it goes down too much, the country can sell parts of its reserves. With crypto, you don't need to worry about government intervention, but short term volatility is the compromise. If you don't think that you can cope with the fluctuations, simply sell any portion of your bitcoin for cash, and keep the rest so that you don't get affected as much.