The stop loss should definitely not be just tucked away in your head. You don't want to wake up in the morning and find that the price has gone well past your mental stop loss.
So if the price does keep going in the wrong direction, while you are saying "it's going to come back", your broker will automatically execute the stop loss when it reaches the price you specified.
Never move a stop loss to where it would be risking more money. Stop losses can be moved in order to lock in profit, or to risk less, but never to risk more.