Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

buying a stock while the price is going down, and buy it at a lower price
If you bought them, you can sell them.  That does not preclude you from buying again later. You might get yourself into a situation where you need to account for a so-called "wash sale" on your taxes, but your broker should calculate that and report it on your 1099-B at the end of the year.  There's nothing illegal about this though - It's just a required step in the accounting of capital gains for tax purposes.