Do not go with someone's prediction and invest believing their prediction. Anything can cause crypto value fluctuate. 2018 has been an year for buying coins with cheap rates and you are aware of this. Trust in bitcoin and crypto coins. Have a complete study, pick the coins you find potential and invest. Just make sure, crypto value fluctuates and none knows when values would spike up or fall back. Prepare and train yourself to be familiar with crypto currencies movement. We have short and long term profitable coins. Choose and abide to the timings accordingly.