The main lesson from the previous crash is that the holding is a bad idea. Volatility of the crypto currencies is very high, therefore the trading is very useful, I think.
While Bitcoin falling I noticed that people who have already sold their crypto currency on the high levels try to dump the markets more deep, posting a bad or even fake news.
That's what I actually learned. I think I believe too much in my coins that's why even I know it's good to sell I still hold and now I loss more than half of it so I just hold it again until I regain my losses. However, I'm still optimistic that when bitcoin will surge again altcoins will follow and I'll change my strategy after I regain my losses. Sometimes holding sucks.