It's not just a bad year you need to be ready for. The decade starting 1999 through end of 2008 returned an average of -1.59% per year as averaged out over the entire decade, and was worse than even the decade from 1929 through 1938. There was a similar bad decade ending in 1975 where the average return was 1.4% per year. The decade ending in 1938 returned 0.7% per year on average, so the Great Depression was actually a better decade than the Great Recession we had recently.

The best trick to surviving a 10-year decline like this is to not be in stocks at the time. You need to realize when to leave. If you plot the 10-year average return on the S&P500 over time, you'll see it follows an approximate 33 year cycle give or take a couple years going back to 1928. The suggests the next bad decade is going to start about 2032, give or take. Once you understand this business cycle, you'll understand when to be in stocks and when to switch to defense and go into gold or bonds. The overheated (bubble) portion of the cycle is when you need to be getting out of the market and headed toward gold. You can tell it's overheated as there will be a lot of volatility as the big players are quietly cashing out, headed toward safer harbors like gold and bonds, meanwhile pumping everyone else up so that everyone wants to be in stocks. Easy credit will be available, for instance home equity lines of credit, that people will be drawing on to invest in the market. There's going to be this feeling of euphoria in the air and everyone is going to be feeling rich.

If you plot the average 10-year return on gold, you'll see it's a cycle that runs opposite to stocks. Normally gold is a horrible investment with volatility higher than the S&P500 and average return of only 3.1% since 1981, but when the stock market is crashing it's best to be in gold. Problem with gold is it peaks in value very quickly, then falls fast. Once the market starts the turn around, it's best to completely dump gold and get back into the market. Gold is a horrible investment the rest of the time.