Oil from USD 110 to USD 27 and back closing to USD 40. Today financial markets are dominated by speculation that drive part a nation economy. The best strategy will always be the same. Know the value of the asset. When price low be brave to buy more and when price high be scary to dispose.
If you find something can have a return of more than 100% in 3 to 5 years. Forget about the volatility and just keep holding it.