My advice to beginners and those who read this post - Sometimes you need to be able to wait, but do not be greedy. Crypto currency is like a drug. Having made the wrong move here you can lose everything. Do not repeat mistakes and learn from someone else's experience. 
And the best part is, you won't be able to do this again.
Yes, if you buy bitcoin, and wait, you could still eventually sell it for gain, but always less than before. Altcoins (that survive) may act in a similar fashion, but in a smaller magnitude. The closer you go back in time to the beginning of bitcoin, the more spectacular gains could be made.
In a retrospective, you should have sold your bitcoin in Dec 2017, bitcoin has yet to reach the value it managed that year. And of course buy when it goes cheap. Now is not such a bad time to buy, but take a look a few years later rather than weeks before selling again...