I just saw this thread and I know you must be smiling now if you bought the dips in December 2018. Almost everywhere is green, at least better than December 2018. Investing in good crypto coins is very profitable, just hold and don't sell when the price is lower.
well, investing in crypto is not always profitable
because its depends on where we drop our money, if we drop our money to a shitcoins, for sure we will lose it buddy
so, many expert will said DYOR before investing

Yes, we have to research ourselves before investing in any coin, we don't know how far the price will recover in the market. Most of the people will not do research before investing and most of the people will invest only hype coins that's why we should always research before investing in any coin.