when you say 1 stock will go down, and that week every single stock goes down- you really shouldn't start a thread about how smart you are.
Im not saying Im smart nor am I saying its exactly 1 stock but rather past experience has shown that 1 stock goes in the red however i keep my loss at 2% usually if in that day the stock has a high volatility and goes up and down I have a risk management system preventing exposure to heavy losses but most of the times if I held the stock a little longer I would have had a gain.