There are so many lessons from the Solyndra story, most of them related to the awful, inevitable consequences of letting politicians invest our money.

But there's a more general lesson here about investing: you should never invest based on promises.

The investment world is full of promises -- promises that would never pass the test of an inquiring mind. But these promises pull on the heart, not on the brain, and that's why you can't afford to let your heart win out over your brain on investments.

That was the lesson of the dot-com busts in the late '90s, when all kinds of tempting, heart-filled promises were made about Internet companies, despite the fact that many of these companies weren't making any money, had management with no business experience, and concealed most of their records. But their promises seemed so appealing that folks ignored the reality.

The reality, of course, led to the tech crash, from which the Nasdaq still has not recovered. 

Investors should avoid empty promises like the plague -- which is why we should always avoid handing our investment money over to politicians, who are the masters of empty promises.

David Asman joined FOX News Channel (FNC) in 1997 and currently serves as host of "Forbes on FOX," a weekend half-hour program that offers an informative look at the business week (Saturday from 11:00-11:30 AM/ET). Asman is also an anchor on FOX Business Network, where he co-hosts "After the Bell" (4-5 PM/ET) with anchor Liz Claman. Click here for more information on David Asman