Risks of mortgaging your primary residence

In his inspiring recount, Pasquale the Swiss Multi-millionaire warns us against “the risks of a mortgage on his private home, and (…) to use a mortgage to (…) take advantage of the current low rates to make his savings grow elsewhere”… which is what I am currently doing.
Can anybody help me understand what these risks are, if the residual debt is below 50% of the commercial value of the estate and as long as the mortgage payments are met ?

A post was merged into an existing topic: Why would an interest increase of 3% jeopardize so many real estate loans?