It is normal for Bitcoin to fluctuate. You can keep holding for a long time, and you can choose to buy Bitcoin when the price drops. Long-term holding requires patience.
If you are a long term holder of bitcoin, its market volatility won't create a hard impact on your coin because even if the price suddenly drops down, bitcoin will always recover. Bitcoin is not free from market volatility but holding it for long might prevent it from losing your investment's profits.
Market volatility will always be present so there's no way we can protect our coins from price fluctuations but if you have taken safety measures to prevent them losing, then we will always witness a good price surge of bitcoin continuously.