A decentralized cryptocurrency in and of itself will never be stable in its price, since they depend on the ratio of supply and demand, which cannot be constant.
However, the concept of a stable cryptocurrency exists. There are special coins that can not bring profit to their holders, as they are, in fact, a digital copy of ordinary currencies and in their price are equal to them. These are USDT, TUSD and others. They perform well a supporting role for working with cryptocurrency and make it much easier. In fact, they serve as a buffer between a cryptocurrency and a common currency, or a sump when it is urgent to withdraw funds from a particular cryptocurrency, but there is no suitable pair, or it’s not time to invest in the right coin.