Recent data released by Comsec listed both Afterpay (ASX: APT)...

Recent data released by Comsec listed both Afterpay (ASX: APT) and a2 Milk (ASX: A2M) in the top 5 most traded stocks two weeks ago with each making up 1.5 per cent of the trading volume. This indicates that retail traders are trying to grab a bargain while they are supposedly cheap, but could they just be catching a falling knife?How far will Afterpay and a2Milk fall?Afterpay has fallen nearly 50 per cent since February and over 21 per cent this calendar year, while the a2 Milk Company has fallen over 50 per cent this calendar year and over 70 per cent since mid-2020. That said, the increased trading on these stocks in recent weeks has halted their fall at least temporarily.When good stocks fall heavily, it is common for investors to do two things: firstly, they attempt to buy a perceived “cheap” stock at what they believe is its lowest price, which is exceedingly hard to do and, secondly, some practice dollar cost averaging, which is an even worse strategy. In the last week, I have had emails from several investors who have taken it upon themselves to practice both of these strategies, which has resulted in them losing money and asking what they should do now.In my opinion, retail investors speculating that a stock has stopped falling by looking at the current share price and comparing it to where it was is a flawed, high risk strategy. When it comes to Afterpay and a2 Milk, neither of these stocks have confirmed they have stopped falling in price and, as such, both stocks are likely to continue to fall.If Afterpay falls below $81, it will likely fall to between $40 and $60 and if a2 Milk falls below $5, it will likely fall to around $2. Unfortunately, if retail investors continue to speculate, it is highly likely they will get caught out.