In my freshman year of 1962, my college roommate pointed out that government debt is different from the money we owe other people. Government bonds amount to just money we owe to ourselves. Fifty years later, I'm in a business that has me explaining that when we borrow from our 401(k) accounts, it is just money we owe to ourselves. Every dime of interest we pay accumulates as part of our plan's annual earnings. The irony of 401(k) loans is that, for much of the past decade, they have been the best-performing asset in retirement plans.