Yes, index funds pursue the same income as the market, and the market has ups and downs. If investors get profits, they can take profits.

Investors can set a profit-taking line. For example, the expected return of the fund is 20%, and it will stop when the profit of the fund reaches 20%. If investors are not sure about the fund's later trend, they can stop the profit by half first, and then stop the profit by half when the fund continues to rise until the fund is sold. When the fund falls, they can all sell the fund.