I would say if you're holding a lot of money in a S&P 500-tracking index fund, switch to holding a total stock market fund instead. It's probably a bad time to hold SP500 right now, but you don't want to get out of the market entirely because there's no way to know when the bubble pops. So hold a total stock market fund instead, so that you don't have an outsize amount of your portfolio invested in the companies leading the SP500 (which are the most likely to lose the most when the bubble pops).