According to CNBC, Jim Cramer said investors can help protect gains in fast-rising stocks by selling half after a parabolic move, warning that such rallies can reverse quickly and that he does not know when they will stop rising. He said Micron fell 12%, Sandisk dropped 22%, and Dell slipped 7% this week after big earlier runs, while money rotated into Amazon, Microsoft and Apple. Cramer said the recent pullback does not change the long-term AI story, but it shows why investors should take profits after outsized gains. He cited Arm Holdings and Corning as examples of extended stocks and said he recently exited Arm for the CNBC Investing Club portfolio and trimmed Corning in several sales in late June.