Stops

[IndexSwing]

I trade NDX options and I have always used mental stops. But the other day my mental stop was hit and I froze and ended up losing much more than I should have. I no longer trust myself and I want to set the stop so that it will execute automatically. Is there any problem with placing a stop order? If the market is close to my stop price do I have to worry about floor traders slightly manipulating the price in order to stop me out?

 

[interdigital]

I don't trade options, but I was trading ETFC on Friday, and the stock was around 3.30 and I had a stop in at 3.27. Then all of a sudden the price spiked down to 3.23 and then immediately spiked back up to 3.30. It triggered my stop and I sold at 3.23! That cost me $500. A mental stop would have prevented that. I thought high volume stocks (like ETFC was on Friday) don't do that, but I guess it can still happen.