The one lesson worth knowing is: "There will always be opportunity". It may not be easy and it may not be fast but the opportunity is there every morning. The place to start is to PAY ATTENTION. That alone will get you into the second quartile.
Take a look at the first decade of the last century in the chart below:

A forty percent drop from 1901 to1903. A 120% up move in the next two years. Followed by a 50% crash in the next 23 months. Wrapping up with a 60% 13 month run to the upside.
Two Panics, a Presidential assassination and an earthquake.
The conditions are different but we'll get through this.
Chart from Dow Jones Indexes.