You bet that bitcoin trading is risky. No one guarantees its value. Only ask and demand does the value. Plus it is new thing, bitcoin users are also sort of labrats.

What if regulators in some main market forbid bitcoin? What if some clearly better alternative shows up? Because one day such thing will most possibly come. What if some hacker does it even worse than with bitfinex? You see, the value could still drop dramatically. Although not likely now or next week, it is always possible. What if some lousy hacker steals your bitcoins too? You can lose all.

So, like gambling, you don't want to invest in bitcoin more than you can afford to lose. With this you have peace in mind, whatever happens.