Just hold. It will not fall.
1. The cryptomarket was cleared off from the fraudulent projects, along with projects that did not stand the market competition. Therefore, now, in 2019, it's not like the Wild West as it was.
2. Cryptocurrency excitement was not a positive phenomenon. It has attracted the attention of millions of people who hoped to get rich without doing anything. Now that sphere is gradually getting rid of people who do not even have basic economic or investment knowledge. And the market is stabilized in that meaning.
3. Institutional investors (banks and hedge funds with a lot of money) use cryptomarket as a variant to diversify their assets. The investment in coins is considered as a more secure investment in the period of volatility of bond markets and gold.
Another question: Where to invest? Just diversify. Part of the portfolio must necessarily be in altcoins (those that have their own blockchain - approved technology, their market, which they want to change), because they can have growth even more than bitcoin. Many of them are really undervalued.