Inflation

I promise if you do this for a while, you will not have any stress.

Some facts: Inflation eats you alive
What cost $5000 in 1970 would cost $22,146.84 in 2000.
What cost $500,000 in 1970 would cost $2,214,684.02 in 2000.
What cost $500000 in 1970 would cost $2,916,144.08 in 2012.
Use an inflation calculator and theory craft about the future money value if you sit on it based on if you invest it.

Go to http://www.marketwatch.com/investing/fund/VTSAX and see what you would have now had you invested that money even during the worst years of the recession. VTSAX is a broadly diversified market that follows the overall stock market.

You are FAR better off investing broadly in the market, DO NOT ATTEMPT TO PICK INDIVIDUAL STOCKS with a sizable percentage of your holding, diversify.