Your right, there is always that possability. But I Know the max moves in the last couple of years in the markets that I trade. I know that those maxs can be exceeeded. So I trade when the probabilities are in my favor, and take it on the nose when things act other than they have in the past. If I have a big loss, I usually try to get flat or slim down the position to go home. I don't take stuff home because i have a loss, I take stuff home because I think that I can make money over night or in the morning. I guess that works kind of like my stop to prevent complete blow out.
If its part of your plan and you've tested it and it works --- it's a good thing. If you're doing it because you're emotionally responding to a trade thats going wrong its a bad thing. On plan=good. Off plan=bad.
It is part of my plan. I do need to get better on not getting emotional, and waiting until the right time to added to my positions. My trading still is a little to much gut feel to be able to create a set of all incompassing rules. I like everyone else in this game, always have room for improvement.