There is good risk and bad risk.
Some types of risks (good risk) increase potential return whereas other types of risks (bad risk) do not increase potential return and thus increase the likelihood of plan failure. Sound risk management entails taking on the appropriate level of the good risk and shunning the bad risk.
Risk and return are related.
The compensation for taking on increased levels of (good) risk is the potential to earn greater returns.
Diversification is key.
Comprehensive, global asset allocation can minimize the risks specific to individual securities.
Capital markets do a good job of fairly pricing all available information and investor expectations about publicly traded securities.
Portfolio structure explains performance.
The asset classes that comprise a portfolio and the risk levels of those asset classes are responsible for most of the variability of portfolio returns.
Investing takes discipline.
The only way to sensibly deal with markets is to have a thoughtful long-term plan and to implement that plan in a disciplined fashion, regardless of emotions or short-term market fluctuations.