Risk is not only limited to Bitcoin but to other investments also like Forex, Stocks etc. We as an investor are not in a position to completely eliminate risk in any investment but what we can do is reduce the impact of risk by adopting strategies that are aimed at mitigating the negative outcomes.
If we look at how Bitcoin has evolved over a period of time then it's quite clear that Bitcoin price has always gone up with period of time. If someone is investing in Bitcoin for shorter duration then he has the risk of losing significant amount of his investment. He has the option to reduce this risk by adopting the strategy of long term investment.
You are correct that risk is not just limited to Bitcoin but it is also part of other investments like Forex and Stocks. As investors we can not make risk disappear completely but we can reduce its effects by using strategies that minimize possible losses. Bitcoin past performance shows that its price has gone up consistently over time. So investors who choose to invest for long time can reduce their risk of losing a lot of money. On the other hand investing in Bitcoin for short time is riskier and can lead to big losses. With investing for long term people can reduce this risk and possibly get more stable returns.