National Debt vs GDP - why does it matter?

[Peatree]

For example, per the "Wall Street Journal"...

"In stark but simple terms, unless Americans are made aware of this financial crisis and demand accountability, the very fabric of our society will be destroyed. Interest rates and interest costs will soar and government revenues will be devoured by interest on the national debt. Eventually, most of what we spend on Social Security, Medicare, education, national defense and much more may have to come from new borrowing, if such funding can be obtained. Left unchecked, this destructive deficit-debt cycle will leave the White House and Congress with either having to default on the national debt or instruct the Treasury to run the printing presses into a policy of hyperinflation."

Does this mean I only have to worry about high interest rates? I don't really use a credit card, and typically pay cash and/or own what I need, so does this effect me or not?