Note that it doesn't matter if you sell wrong, but don't buy wrong. It's better not to buy than not to sell. However, sometimes it doesn't matter if you are trapped, especially if you are still optimistic about the medium and long term. Appropriate short-term trading can reduce the cost, which is equivalent to buying at the right position. However, this requires practice and continuous summary.
Experts can do short-term trading when it is necessary to do short-term trading, long-term trading when it is necessary to do long-term trading, and can control positions. Position management is actually the most critical. How much to sell and how much to buy is more important than the buying and selling points. However, this does not mean much for small funds.