The market in 2018 is going up and down, not stable almost all the time the market has a downtrend. But in recent days, the market was suddenly rising up, and at now the BTC price surpasses $4,000 and ETH reach near $120. I think that now is the bull run of the cryptocurrency market and I guess that the rate will improve at the beginning of 2019.
Bitcoin price in 2018 mainly went down. In 2019 it will go up and down and up and down a lot. Not with huge swings and volatility. It will be mainly stable but Bitcoin should be worth more at end of 2019 then at start.