Tricky questions and this kind of thread will be actual in the next bull run. What we should have done before the last bull market is the same thing that we have to do in the recent market. The bull market will become a reality sooner or later but as an investor, we need to reconsider the realities one more time before it is too late. Investing and diversifying among the best altcoins and waiting patiently will not make anyone upset.
Why would this be a tricky question? Its easy, the best thing we could do is to sell all we got in 2017, I mean all coins and tokens, in that year most of them were pumped, the ones that worth and others too. In 2018 we saw a huge dump, that would be a great entry point, so you would have a lot of money to buy at a discount, what ever you wish and to start fresh.
What should we learn from the past is that we should dump on top, like whales do and to get in again when price drops.