SMI has always believed that helping investors form realistic expectations is important to their long-term success. That's because investing success is primarily driven by controlling one's emotions, and knowing what's reasonable to expect helps immensely in that regard.
For example, if you know that the stock market experiences a 10% correction roughly every 18 months, you're much less likely to freak out and sell stocks when they've suddenly dropped 12% for the first time in two years. If you don't know that historical pattern, you're more likely to make an emotional mistake in that scenario. Make enough of those emotional mistakes and they start to seriously compromise your long-term returns.