It doesn't matter how sure an investment is do not put in what you can't afford to lose even if life is all about taking risks you should make sure that your risks are well managed and calculated. If you want to invest in Bitcoin or alt coins it's not adviced to invest more than 40 percent of what you have, making just a single investment isn't a wise thing to do, it's better to spread those investment just incase one or two doesn't work out, do not put all your eggs in one basket so you won't get disappointed, this is a very common mistake a lot of people make
I do not believe in investing what I can afford to lose because I don't have any money I'm willing to lose and if I know I will lose money, I will never invest in that business. My mindset is to invest what I can hold for long, for Bitcoin investment. Every investment have associated risk, no doubt about it but the truth is that the risk of investing in Bitcoin is greatly reduced if the investment is planned in such a way that it can be held for a long time. Bitcoin price move in cycle as we have seen over a decade now so any investment that can be held between the market cycle of 4 years will sure yield good profits.