Today's market performance, opening high but closing lower, was within expectations. During the session, the ChiNext Index reached its highest point in the last decade, yet it experienced the most significant decline. This phenomenon and its underlying causes will be analyzed through backtesting in this article. Among the major broad-based indices, the SSE 50 led gains with an increase of 0.34%, followed by the STAR 50, which rose by 0.09%. Conversely, the ChiNext Index led the declines, dropping by 1.22%, while the Micro-cap Stock Index fell by 0.85%. Within the Shenwan primary industry indices, Pharmaceuticals & Biotechnology led the advancers with a gain of 1.45%, followed by Banks, up 1.11%, and Household Appliances, which increased by 0.67%. The leading decliners were Basic Chemicals, down 1.74%, Real Estate, falling 1.56%, and Conglomerates, which dropped 1.47%. A total of 1,701 stocks advanced, while 3,387 declined, resulting in a median price change of -0.70%. Fourteen stocks, including Hangjin Technology and Guangdong Hongtu, hit new one-year lows during the session. Among these, two stocks, including *ST Panda, reached new all-time lows. In contrast, 139 stocks, such as Contemporary Amperex Technology and Zhongji Innolight, reached new one-year highs. Of these, 66 stocks, including Dongshan Precision and Luxshare-ICT, achieved new historical highs. Fifteen stocks, including Gusheng Technology and Furong Group, fell by the daily limit. Meanwhile, 68 stocks, including Songfa Shares and Jibei Te, rose by the daily limit. The average increase for 340 convertible bonds was 0.24%, while their underlying stocks averaged a decline of 0.04%. My portfolio of 20 convertible bonds averaged a gain of 0.45%, with their corresponding underlying stocks averaging an increase of 1.50%. Today, I sold Jingrui Convertible Bond 2, Yirui Convertible Bond, and Diou Convertible Bond, and purchased Jingneng Convertible Bond, Mona Convertible Bond, and Bairun Convertible Bond. The final account showed a total increase of 0.51%. It was a rare occasion where the portfolio outperformed the equal-weighted convertible bond index during an upward movement, primarily driven by gains in Shuyu Convertible Bond (2.89%), Diou Convertible Bond (1.64%), Zhengchuan Convertible Bond (1.60%), and Baiyang Convertible Bond (1.29%). A question was raised online: would buying the stocks that hit new one-year or historical highs, as frequently mentioned, yield substantial profits? We conducted a backtest covering the period from April 14, 2016, to April 14, 2026. To eliminate the impact of commissions, they were set to zero. The strategy involved rotating portfolios of stocks that had recently hit new one-year highs or historical highs at intervals of 1 day, 10 days, 20 days, and 60 days. The backtest results were startling. The worst-performing strategy involved selecting stocks at one-year highs with daily rotation, resulting in a loss of 99.82% over ten years, with annual losses every year. Even the least severe loss, in 2021, was 7.81%. A relatively better approach was selecting stocks at historical highs with a 20-day rotation, yielding a cumulative return of 3.52% over ten years. After deducting commissions and other fees, it is likely that no profit would remain. The more favorable years were 2019, 2020, and 2025, where the annual returns for the historical highs strategy with a 20-day rotation were as high as 65.29%, 62.99%, and 101.51%, respectively. However, it is impossible to predict in advance whether the market will be bullish or bearish. Why do stocks often decline after reaching new highs? The analysis suggests that once a new high is achieved, almost all holders are in a profitable position, leading many to realize gains and secure profits. Generally, after hitting a new high, a pullback is often necessary to build momentum for further gains. However, the timing and extent of this pullback depend on the ongoing battle between buyers and sellers.