What Happened on my big loss

I was long, 18 contracts (equivalent to like 18,000 shares of IWM) with and avg. price of 837, exited 2 at 838 at my signal, but didn't have in a stop, then the drop happened. I never added to the position on the way down, I was long in the morning and didn't have a stop. I exited 10 at 828.5 because I had to leave for work. I never had in a stop. I left on another 6 contracts overnight and covered at 823.1. Today the high of the day was 837. OUCH! What happened. I had to leave for work, that's what happened. Just like today, I was long and had to leave for work. I ended up breakeven after making 1k in the morning. Work,,,Work, Work............I'm sure I will bounce back, the fact that I lost so much in one day is disturbing. I've read all the trading books, Trading in the zone included. This month was different then last month because I've been trying to use large size, but I can't trade the same way with large size, and as a result I have had some big losing days these last few weeks. So I need to switch up my style and go back to what I was doing before, becuase my trade management before never would have let a loss this big occur, because I was using stops before. It's going to be hard trading small size again, but it is the only way for me to get back on my feet.