Thanks for the replies.

Yes it was definitely greed, and because I decided to open a huge eth short when I thought I knew exactly what was going to happen, because i'd already been  right 5 times in a row on each 10% move. I think it was something like 250,000 contracts short on eth at $270.

Difficult taking such a big loss for me, but I'll start again at some point with 0.1...  Although I know it would be very difficult to replicate.