The core of investing is "not to lose the principal," not "chasing the last penny."

Every time the U.S. stock market hits a new historical high, it will eventually reach even higher highs, but there will always be pullbacks in between. No one can precisely buy at the bottom and sell at the top. Your current strategy, which prioritizes the safety of your principal, is completely correct. There's no need to risk getting trapped at a high price just to capture the last bit of gains.