By Steve Cordasco and Jason MardinlyNEW YORK ( TheStreet) -- One of the worst mistakes I see investors make is to automatically equate investment performance with total account value. They tear open the monthly statement, look at the principal and immediately judge the performance of their investments based on which way the bottom line moved. Then they compound that mistake by making reallocation decisions based on this information in an attempt to "fix" the perceived problem (or chase illusory profits). KMG) and Lockheed Martin ( LMT) helped offset some of the price decline. In 2008, KMG paid more in 2008, $3.89 per share, vs. 2007's $3.36. In 2012 KMG paid dividends of $4.85 per share, more than outpacing the federal government's reported amount of inflation. Likewise, Lockheed paid $1.42 in 2007 dividends but $1.83 in 2008. In 2012 Lockheed paid common shareholders a whopping $4.12 per share in cash dividends. The monthly (or quarterly) statement shows more than just the account summary; it also has an income summary, which includes dividends earned.