It is fundamentally a MISMEASUREMENT issue. Only tangible items (much like a company's accounts) are measured in net worth (on the asset side: cash, investments, property, cars, etc and on the liabilities side: credit card debt, student loans, mortgages, personal loans, etc). The biggest missing element (which will be relatively more important in magnitude for younger people) is HUMAN CAPITAL. This is not included in a net worth calculation typically. For an even more start example, consider a new university graduate who has nearly zero financial or other assets and a massive debt load. Does that person have negative net worth (properly measured)? Not at all. That's what the comment of "nothing to be afraid of" means.