Average Investors often lack discipline and let their emotions drive investment decisions. They tend to wait for investment returns before getting in and jump ship before things take off (i.e. buy high and sell low). Here is a simple chart recently distributed from JP Morgan further illustrating this common behavioral mistake.
The best recipe for success is to have an investment portfolio consistent with your financial plan. Then commit and stick with your plan for years. We've seen a lot of these charts over the years but this one really shows how much money average investors are leaving on the table.