My advice is that, when you are investing (especially for retirement), put all your money into an S&P 500 Index Fund. (Of course, having said that, I am also going to make the case in the next section for investing in an ESG Fund.) In the last chapter, I showed you that this will return you an average annual return of 10.1% per year. That return from 1926 to 2018 included both the bear and the bull markets. Of course, you must have the patience to endure recessions and not panic and sell stocks when it enters a bear market. This panic is the hallmark mistake of amateur investors.
However, recessions are a short run phenomenon. We have had 12 recessions (and expansions) since the end of World War II, including the current Pandemic Recession. The average length of these recessions has been 11 months. As long as you are not within five years of retirement, you have the time to ride out the recession and achieve your 10.1% annual return. One more note, if you want to be risky and try your own luck at the stock markets, do not invest any more than ten percent of your current cash/stocks in the market. If you make a big mistake, you can recover from a ten percent loss.