In 1988 he wanted to buy 30 million (split-adjusted) shares in Federal National Mortgage Association (Fannie Mae), which would have cost around $350 million.
"After we bought about 7 million shares, the price began to climb. In frustration, I stopped buying ... In an even sillier move, I surrendered to my distaste for holding small positions and sold the 7 million shares we owned."
In October 1993, he told Forbes that "he left $2 billion on the table by selling Fannie Mae too early. He bought too little and sold too early. "It was easy to analyze. It was within my circle of competence. And for one reason or another, I quit. I wish I could give you a good answer."
This was a mistake that, he wrote, "thankfully, I did not repeat when Coca-Cola stock rose similarly during our purchase program which began later the same year.