I cannot lose any of my initial investment anymore as I also earned that back 5-fold. I am now playing with "house money". Sure money is money, so if I lose this I will be sad... for a day.
But that is highly unlikely. While I do not know if bitcoin will ever be a useful currency, frankly, I don't care. Just trade the ---- thing as long as the customer demand is there. :) (And if you make some good money, just take it of the table)