Sort:  

Nothing is guaranteed. It is a common investment strategy, but if you were guaranteed to always make money, everyone would do it. It is meant more as managing risk while maximizing returns.

@ahyar94 what do you mean?

if we buy bitcoint, whether it will be able to convince the future..

Bitcoin have risks, but you can use this strategy to everything :-) Diversifying your portfolio is also important.

I will try, thank you for the information @rafaljakobsen