New Delhi, May 8 -- When I meet people who've just been sold an expensive insurance policy or a dubious mutual fund scheme, I'm reminded of a simple truth that has taken me decades to fully appreciate: in financial services, the best way to get what you deserve is to assume the other party doesn't deserve your trust.

For three decades, I have observed the machinery of banks, insurance companies, and investment firms with growing concern. The conventional wisdom suggests that a positive, trusting attitude leads to success in life. We're taught from childhood that assuming the best about others usually works out well. This approach serves us admirably in most human interactions--except when buying financial products.

This reveals an uncom...