Profit turned into loss

Today, Hong Kong stocks plummeted again. Many individual stocks were bloodwashed. Some stocks initially rose and were bought yesterday $AVICHINA (02357.HK)$ It rose by more than 5% shortly after opening, and fell 3.66% at the end of the day. Actually, I had a lot of time to sell while still being profitable, but in the end I ended up selling with a stop-loss
Sometimes I admonish other shareholders not to turn profits into losses; I myself am repeating this kind of low-level mistake.