There is a really great article in The Atlantic (from 2011) called "Secret Fears of the Super-Rich" on this topic:
Excerpt: The respondents turn out to be a generally dissatisfied lot, whose money has contributed to deep anxieties involving love, work, and family. Indeed, they are frequently dissatisfied even with their sizable fortunes. Most of them still do not consider themselves financially secure; for that, they say, they would require on average one-quarter more wealth than they currently possess. (Remember: this is a population with assets in the tens of millions of dollars and above.)
Excerpt: The respondents turn out to be a generally dissatisfied lot, whose money has contributed to deep anxieties involving love, work, and family. Indeed, they are frequently dissatisfied even with their sizable fortunes. Most of them still do not consider themselves financially secure; for that, they say, they would require on average one-quarter more wealth than they currently possess. (Remember: this is a population with assets in the tens of millions of dollars and above.)
Link: http://www.theatlantic.com/magazine/archive/2011/04/secret-f...