If the stock dips too much, the active investor will have a tendency to think that the stock will turn around any day now. This is typically known as marrying a stock. They love it, they're loyal to it, and most of the time if they marry it, they lose it. The active investor will typically make 5 to 10 trades a week. The day trader takes the most risk.
Day traders like to buy on the momentum of the stock.
If it's rising, they buy. If it levels off, they sell. If a stock drops instead of rising, they'll sell immediately in an attempt to cut their losses. Typically, beginning day traders do very little research. They tend to listen to chat-room hypesters, and end up buying stocks at the wrong end of the price curve.