Historian and author Edward Gibbon had enough. He declared himself wealthy when, in his memoirs, he wrote, "I am indeed rich, since my income is superior to my expense, and my expense is superior to my wishes."

Now there's a wise, content, and rich man, you may be thinking. But note that he could be billionaire or beggar. We don't know his fortune, only his self–assessment. Would you rather be rich or content? Could you be both? Maybe you already are. If not, include contentment in your personal investing plans.