The phrase 'a sharp rise must be followed by a fall' is a common phenomenon description in the investment market, mainly referring to the situation where prices (such as stock prices, commodity prices, etc.) often experience a decline after rapidly rising to a certain high level.

This phenomenon is usually related to factors such as market supply and demand, and investor psychology:

1. When prices rise rapidly, investors who have made profits earlier may choose to sell to realize gains, leading to increased selling pressure;

2. At high levels, new investors may reduce buying due to concerns about risk, resulting in insufficient buying interest;

3. At the same time, market sentiment may shift from exuberance to caution, further pushing prices down.

However, this is not an absolute rule; it is merely a common market behavior, and actual trends will also be influenced by various factors such as the macro environment and fundamentals.